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perlvar ()
  • >> perlvar (1) ( Solaris man: Команды и прикладные программы пользовательского уровня )
  • perlvar (1) ( Разные man: Команды и прикладные программы пользовательского уровня )
  • 
    
    

    NAME

         perlvar - Perl predefined variables
    
    
    

    DESCRIPTION

         Predefined Names
    
         The following names have special meaning to Perl.  Most
         punctuation names have reasonable mnemonics, or analogs in
         the shells.  Nevertheless, if you wish to use long variable
         names, you need only say
    
             use English;
    
         at the top of your program.  This will alias all the short
         names to the long names in the current package.  Some even
         have medium names, generally borrowed from awk.
    
         If you don't mind the performance hit, variables that depend
         on the currently selected filehandle may instead be set by
         calling an appropriate object method on the IO::Handle
         object.  (Summary lines below for this contain the word
         HANDLE.)  First you must say
    
             use IO::Handle;
    
         after which you may use either
    
             method HANDLE EXPR
    
         or more safely,
    
             HANDLE->method(EXPR)
    
         Each method returns the old value of the IO::Handle
         attribute.  The methods each take an optional EXPR, which if
         supplied specifies the new value for the IO::Handle
         attribute in question.  If not supplied, most methods do
         nothing to the current value--except for autoflush(), which
         will assume a 1 for you, just to be different.  Because
         loading in the IO::Handle class is an expensive operation,
         you should learn how to use the regular built-in variables.
    
         A few of these variables are considered "read-only".  This
         means that if you try to assign to this variable, either
         directly or indirectly through a reference, you'll raise a
         run-time exception.
    
         The following list is ordered by scalar variables first,
         then the arrays, then the hashes.
    
         $ARG
    
         $_      The default input and pattern-searching space.  The
                 following pairs are equivalent:
    
                     while (<>) {...}    # equivalent only in while!
                     while (defined($_ = <>)) {...}
    
                     /^Subject:/
                     $_ =~ /^Subject:/
    
                     tr/a-z/A-Z/
                     $_ =~ tr/a-z/A-Z/
    
                     chomp
                     chomp($_)
    
                 Here are the places where Perl will assume $_ even
                 if you don't use it:
    
                 o  Various unary functions, including functions like
                    ord() and int(), as well as the all file tests
                    (`-f', `-d') except for `-t', which defaults to
                    STDIN.
    
                 o  Various list functions like print() and unlink().
    
                 o  The pattern matching operations `m//', `s///',
                    and `tr///' when used without an `=~' operator.
    
                 o  The default iterator variable in a `foreach' loop
                    if no other variable is supplied.
    
                 o  The implicit iterator variable in the grep() and
                    map() functions.
    
                 o  The default place to put an input record when a
                    `<FH>' operation's result is tested by itself as
                    the sole criterion of a `while' test.  Outside a
                    `while' test, this will not happen.
    
                 (Mnemonic: underline is understood in certain
                 operations.)
    
         $<digits>
                 Contains the subpattern from the corresponding set
                 of capturing parentheses from the last pattern
                 match, not counting patterns matched in nested
                 blocks that have been exited already.  (Mnemonic:
                 like \digits.)  These variables are all read-only
                 and dynamically scoped to the current BLOCK.
    
         $MATCH
    
         $&      The string matched by the last successful pattern
                 match (not counting any matches hidden within a
                 BLOCK or eval() enclosed by the current BLOCK).
                 (Mnemonic: like & in some editors.)  This variable
                 is read-only and dynamically scoped to the current
                 BLOCK.
    
                 The use of this variable anywhere in a program
                 imposes a considerable performance penalty on all
                 regular expression matches.  See the BUGS manpage.
    
         $PREMATCH
    
         $`      The string preceding whatever was matched by the
                 last successful pattern match (not counting any
                 matches hidden within a BLOCK or eval enclosed by
                 the current BLOCK).  (Mnemonic: ``' often precedes a
                 quoted string.)  This variable is read-only.
    
                 The use of this variable anywhere in a program
                 imposes a considerable performance penalty on all
                 regular expression matches.  See the BUGS manpage.
    
         $POSTMATCH
    
         $'      The string following whatever was matched by the
                 last successful pattern match (not counting any
                 matches hidden within a BLOCK or eval() enclosed by
                 the current BLOCK).  (Mnemonic: `'' often follows a
                 quoted string.)  Example:
    
                     $_ = 'abcdefghi';
                     /def/;
                     print "$`:$&:$'\n";         # prints abc:def:ghi
    
                 This variable is read-only and dynamically scoped to
                 the current BLOCK.
    
                 The use of this variable anywhere in a program
                 imposes a considerable performance penalty on all
                 regular expression matches.  See the BUGS manpage.
    
         $LAST_PAREN_MATCH
    
         $+      The last bracket matched by the last search pattern.
                 This is useful if you don't know which one of a set
                 of alternative patterns matched.  For example:
    
                     /Version: (.*)|Revision: (.*)/ && ($rev = $+);
    
                 (Mnemonic: be positive and forward looking.)  This
                 variable is read-only and dynamically scoped to the
                 current BLOCK.
    
         @+      This array holds the offsets of the ends of the last
                 successful submatches in the currently active
                 dynamic scope.  `$+[0]' is the offset into the
                 string of the end of the entire match.  This is the
                 same value as what the `pos' function returns when
                 called on the variable that was matched against.
                 The nth element of this array holds the offset of
                 the nth submatch, so `$+[1]' is the offset past
                 where $1 ends, `$+[2]' the offset past where $2
                 ends, and so on.  You can use `$#+' to determine how
                 many subgroups were in the last successful match.
                 See the examples given for the `@-' variable.
    
         $MULTILINE_MATCHING
    
         $*      Set to 1 to do multi-line matching within a string,
                 0 to tell Perl that it can assume that strings
                 contain a single line, for the purpose of optimizing
                 pattern matches.  Pattern matches on strings
                 containing multiple newlines can produce confusing
                 results when `$*' is 0.  Default is 0.  (Mnemonic: *
                 matches multiple things.)  This variable influences
                 the interpretation of only `^' and `$'.  A literal
                 newline can be searched for even when `$* == 0'.
    
                 Use of `$*' is deprecated in modern Perl, supplanted
                 by the `/s' and `/m' modifiers on pattern matching.
    
         input_line_number HANDLE EXPR
    
         $INPUT_LINE_NUMBER
    
         $NR
    
         $.      The current input record number for the last file
                 handle from which you just read() (or called a
                 `seek' or `tell' on).  The value may be different
                 from the actual physical line number in the file,
                 depending on what notion of "line" is in effect--see
                 `$/' on how to change that.  An explicit close on a
                 filehandle resets the line number.  Because `<>'
                 never does an explicit close, line numbers increase
                 across ARGV files (but see examples in the eof entry
                 in the perlfunc manpage).  Consider this variable
                 read-only: setting it does not reposition the seek
                 pointer; you'll have to do that on your own.
                 Localizing `$.'  has the effect of also localizing
                 Perl's notion of "the last read filehandle".
                 (Mnemonic: many programs use "." to mean the current
                 line number.)
    
         input_record_separator HANDLE EXPR
    
         $INPUT_RECORD_SEPARATOR
    
         $RS
    
         $/      The input record separator, newline by default.
                 This influences Perl's idea of what a "line" is.
                 Works like awk's RS variable, including treating
                 empty lines as a terminator if set to the null
                 string.  (An empty line cannot contain any spaces or
                 tabs.)  You may set it to a multi-character string
                 to match a multi-character terminator, or to `undef'
                 to read through the end of file.  Setting it to
                 `"\n\n"' means something slightly different than
                 setting to `""', if the file contains consecutive
                 empty lines.  Setting to `""' will treat two or more
                 consecutive empty lines as a single empty line.
                 Setting to `"\n\n"' will blindly assume that the
                 next input character belongs to the next paragraph,
                 even if it's a newline.  (Mnemonic: / delimits line
                 boundaries when quoting poetry.)
    
                     undef $/;           # enable "slurp" mode
                     $_ = <FH>;          # whole file now here
                     s/\n[ \t]+/ /g;
    
                 Remember: the value of `$/' is a string, not a
                 regex.  awk has to be better for something. :-)
    
                 Setting `$/' to a reference to an integer, scalar
                 containing an integer, or scalar that's convertible
                 to an integer will attempt to read records instead
                 of lines, with the maximum record size being the
                 referenced integer.  So this:
    
                     $/ = \32768; # or \"32768", or \$var_containing_32768
                     open(FILE, $myfile);
                     $_ = <FILE>;
    
                 will read a record of no more than 32768 bytes from
                 FILE.  If you're not reading from a record-oriented
                 file (or your OS doesn't have record-oriented
                 files), then you'll likely get a full chunk of data
                 with every read.  If a record is larger than the
                 record size you've set, you'll get the record back
                 in pieces.
    
                 On VMS, record reads are done with the equivalent of
                 `sysread', so it's best not to mix record and non-
                 record reads on the same file.  (This is unlikely to
                 be a problem, because any file you'd want to read in
                 record mode is probably unusable in line mode.)
                 Non-VMS systems do normal I/O, so it's safe to mix
                 record and non-record reads of a file.
    
                 See also the Newlines entry in the perlport manpage.
                 Also see `$.'.
    
         autoflush HANDLE EXPR
    
         $OUTPUT_AUTOFLUSH
    
         $|      If set to nonzero, forces a flush right away and
                 after every write or print on the currently selected
                 output channel.  Default is 0 (regardless of whether
                 the channel is really buffered by the system or not;
                 `$|' tells you only whether you've asked Perl
                 explicitly to flush after each write).  STDOUT will
                 typically be line buffered if output is to the
                 terminal and block buffered otherwise.  Setting this
                 variable is useful primarily when you are outputting
                 to a pipe or socket, such as when you are running a
                 Perl program under rsh and want to see the output as
                 it's happening.  This has no effect on input
                 buffering.  See the getc entry in the perlfunc
                 manpage for that.  (Mnemonic: when you want your
                 pipes to be piping hot.)
    
         output_field_separator HANDLE EXPR
    
         $OUTPUT_FIELD_SEPARATOR
    
         $OFS
    
         $,      The output field separator for the print operator.
                 Ordinarily the print operator simply prints out its
                 arguments without further adornment.  To get
                 behavior more like awk, set this variable as you
                 would set awk's OFS variable to specify what is
                 printed between fields.  (Mnemonic: what is printed
                 when there is a "," in your print statement.)
    
         output_record_separator HANDLE EXPR
    
         $OUTPUT_RECORD_SEPARATOR
    
         $ORS
    
         $\      The output record separator for the print operator.
                 Ordinarily the print operator simply prints out its
                 arguments as is, with no trailing newline or other
                 end-of-record string added.  To get behavior more
                 like awk, set this variable as you would set awk's
                 ORS variable to specify what is printed at the end
                 of the print.  (Mnemonic: you set `$\' instead of
                 adding "\n" at the end of the print.  Also, it's
                 just like `$/', but it's what you get "back" from
                 Perl.)
    
         $LIST_SEPARATOR
    
         $"      This is like `$,' except that it applies to array
                 and slice values interpolated into a double-quoted
                 string (or similar interpreted string).  Default is
                 a space.  (Mnemonic: obvious, I think.)
    
         $SUBSCRIPT_SEPARATOR
    
         $SUBSEP
    
         $;      The subscript separator for multidimensional array
                 emulation.  If you refer to a hash element as
    
                     $foo{$a,$b,$c}
    
                 it really means
    
                     $foo{join($;, $a, $b, $c)}
    
                 But don't put
    
                     @foo{$a,$b,$c}      # a slice--note the @
    
                 which means
    
                     ($foo{$a},$foo{$b},$foo{$c})
    
                 Default is "\034", the same as SUBSEP in awk.  If
                 your keys contain binary data there might not be any
                 safe value for `$;'.  (Mnemonic: comma (the
                 syntactic subscript separator) is a semi-semicolon.
                 Yeah, I know, it's pretty lame, but `$,' is already
                 taken for something more important.)
    
                 Consider using "real" multidimensional arrays as
                 described in the perllol manpage.
    
         $OFMT
    
         $#      The output format for printed numbers.  This
                 variable is a half-hearted attempt to emulate awk's
                 OFMT variable.  There are times, however, when awk
                 and Perl have differing notions of what counts as
                 numeric.  The initial value is "%.ng", where n is
                 the value of the macro DBL_DIG from your system's
                 float.h.  This is different from awk's default OFMT
                 setting of "%.6g", so you need to set `$#'
                 explicitly to get awk's value.  (Mnemonic: # is the
                 number sign.)
    
                 Use of `$#' is deprecated.
    
         format_page_number HANDLE EXPR
    
         $FORMAT_PAGE_NUMBER
    
         $%      The current page number of the currently selected
                 output channel.  Used with formats.  (Mnemonic: % is
                 page number in nroff.)
    
         format_lines_per_page HANDLE EXPR
    
         $FORMAT_LINES_PER_PAGE
    
         $=      The current page length (printable lines) of the
                 currently selected output channel.  Default is 60.
                 Used with formats.  (Mnemonic: = has horizontal
                 lines.)
    
         format_lines_left HANDLE EXPR
    
         $FORMAT_LINES_LEFT
    
         $-      The number of lines left on the page of the
                 currently selected output channel. Used with
                 formats.  (Mnemonic: lines_on_page - lines_printed.)
    
         @-      $-[0] is the offset of the start of the last
                 successful match.  `$-['n`]' is the offset of the
                 start of the substring matched by n-th subpattern,
                 or undef if the subpattern did not match.
    
                 Thus after a match against $_, $& coincides with
                 `substr $_, $-[0], $+[0] - $-[0]'.  Similarly, `$'n
                 coincides with `substr $_, $-['n`], $+['n`] -
                 $-['n`]' if `$-['n`]' is defined, and $+ coincides
                 with `substr $_, $-[$#-], $+[$#-]'.  One can use
                 `$#-' to find the last matched subgroup in the last
                 successful match.  Contrast with `$#+', the number
                 of subgroups in the regular expression.  Compare
                 with `@+'.
    
                 This array holds the offsets of the beginnings of
                 the last successful submatches in the currently
                 active dynamic scope.  `$-[0]' is the offset into
                 the string of the beginning of the entire match.
                 The nth element of this array holds the offset of
                 the nth submatch, so `$+[1]' is the offset where $1
                 begins, `$+[2]' the offset where $2 begins, and so
                 on.  You can use `$#-' to determine how many
                 subgroups were in the last successful match.
                 Compare with the `@+' variable.
    
                 After a match against some variable $var:
    
                 `$`' is the same as `substr($var, 0, $-[0]')
    
                 `$&' is the same as `substr($var, $-[0], $+[0] - $-[0]')
    
                 `$'' is the same as `substr($var, $+[0]')
    
                 `$1' is the same as `substr($var, $-[1], $+[1] - $-[1])'
    
                 `$2' is the same as `substr($var, $-[2], $+[2] - $-[2])'
    
                 `$3' is the same as `substr $var, $-[3], $+[3] - $-[3]')
    
         format_name HANDLE EXPR
    
         $FORMAT_NAME
    
         $~      The name of the current report format for the
                 currently selected output channel.  Default is the
                 name of the filehandle.  (Mnemonic: brother to
                 `$^'.)
    
         format_top_name HANDLE EXPR
    
         $FORMAT_TOP_NAME
    
         $^      The name of the current top-of-page format for the
                 currently selected output channel.  Default is the
                 name of the filehandle with _TOP appended.
                 (Mnemonic: points to top of page.)
    
         format_line_break_characters HANDLE EXPR
    
         $FORMAT_LINE_BREAK_CHARACTERS
    
         $:      The current set of characters after which a string
                 may be broken to fill continuation fields (starting
                 with ^) in a format.  Default is " \n-", to break on
                 whitespace or hyphens.  (Mnemonic: a "colon" in
                 poetry is a part of a line.)
    
         format_formfeed HANDLE EXPR
    
         $FORMAT_FORMFEED
    
         $^L     What formats output as a form feed.  Default is \f.
    
         $ACCUMULATOR
    
         $^A     The current value of the write() accumulator for
                 format() lines.  A format contains formline() calls
                 that put their result into `$^A'.  After calling its
                 format, write() prints out the contents of `$^A' and
                 empties.  So you never really see the contents of
                 `$^A' unless you call formline() yourself and then
                 look at it.  See the perlform manpage and the
                 formline() entry in the perlfunc manpage.
    
         $CHILD_ERROR
    
         $?      The status returned by the last pipe close, backtick
                 (```') command, successful call to wait() or
                 waitpid(), or from the system() operator.  This is
                 just the 16-bit status word returned by the wait()
                 system call (or else is made up to look like it).
                 Thus, the exit value of the subprocess is really
                 (`$? >> 8'), and `$? & 127' gives which signal, if
                 any, the process died from, and `$? & 128' reports
                 whether there was a core dump.  (Mnemonic:  similar
                 to sh and ksh.)
    
                 Additionally, if the `h_errno' variable is supported
                 in C, its value is returned via $? if any
                 `gethost*()' function fails.
    
                 If you have installed a signal handler for
                 `SIGCHLD', the value of `$?' will usually be wrong
                 outside that handler.
    
                 Inside an `END' subroutine `$?' contains the value
                 that is going to be given to `exit()'.  You can
                 modify `$?' in an `END' subroutine to change the
                 exit status of your program.  For example:
    
                     END {
                         $? = 1 if $? == 255;  # die would make it 255
                     }
    
                 Under VMS, the pragma `use vmsish 'status'' makes
                 `$?' reflect the actual VMS exit status, instead of
                 the default emulation of POSIX status.
    
                 Also see the Error Indicators entry elsewhere in
                 this document.
    
         $OS_ERROR
    
         $ERRNO
    
         $!      If used numerically, yields the current value of the
                 C `errno' variable, with all the usual caveats.
                 (This means that you shouldn't depend on the value
                 of `$!' to be anything in particular unless you've
                 gotten a specific error return indicating a system
                 error.)  If used an a string, yields the
                 corresponding system error string.  You can assign a
                 number to `$!' to set errno if, for instance, you
                 want `"$!"' to return the string for error n, or you
                 want to set the exit value for the die() operator.
                 (Mnemonic: What just went bang?)
    
                 Also see the Error Indicators entry elsewhere in
                 this document.
    
         $EXTENDED_OS_ERROR
    
         $^E     Error information specific to the current operating
                 system.  At the moment, this differs from `$!' under
                 only VMS, OS/2, and Win32 (and for MacPerl).  On all
                 other platforms, `$^E' is always just the same as
                 `$!'.
    
                 Under VMS, `$^E' provides the VMS status value from
                 the last system error.  This is more specific
                 information about the last system error than that
                 provided by `$!'.  This is particularly important
                 when `$!' is set to EVMSERR.
    
                 Under OS/2, `$^E' is set to the error code of the
                 last call to OS/2 API either via CRT, or directly
                 from perl.
    
                 Under Win32, `$^E' always returns the last error
                 information reported by the Win32 call
                 `GetLastError()' which describes the last error from
                 within the Win32 API.  Most Win32-specific code will
                 report errors via `$^E'.  ANSI C and Unix-like calls
                 set `errno' and so most portable Perl code will
                 report errors via `$!'.
    
                 Caveats mentioned in the description of `$!'
                 generally apply to `$^E', also.  (Mnemonic: Extra
                 error explanation.)
    
                 Also see the Error Indicators entry elsewhere in
                 this document.
    
         $EVAL_ERROR
    
         $@      The Perl syntax error message from the last eval()
                 operator.  If null, the last eval() parsed and
                 executed correctly (although the operations you
                 invoked may have failed in the normal fashion).
                 (Mnemonic: Where was the syntax error "at"?)
    
                 Warning messages are not collected in this variable.
                 You can, however, set up a routine to process
                 warnings by setting `$SIG{__WARN__}' as described
                 below.
    
                 Also see the Error Indicators entry elsewhere in
                 this document.
    
         $PROCESS_ID
    
         $PID
    
         $$      The process number of the Perl running this script.
                 You should consider this variable read-only,
                 although it will be altered across fork() calls.
                 (Mnemonic: same as shells.)
    
         $REAL_USER_ID
    
         $UID
    
         $<      The real uid of this process.  (Mnemonic: it's the
                 uid you came from, if you're running setuid.)
    
         $EFFECTIVE_USER_ID
    
         $EUID
    
         $>      The effective uid of this process.  Example:
    
                     $< = $>;            # set real to effective uid
                     ($<,$>) = ($>,$<);  # swap real and effective uid
    
                 (Mnemonic: it's the uid you went to, if you're
                 running setuid.)  `$<' and `$>' can be swapped only
                 on machines supporting setreuid().
    
         $REAL_GROUP_ID
    
         $GID
    
         $(      The real gid of this process.  If you are on a
                 machine that supports membership in multiple groups
                 simultaneously, gives a space separated list of
                 groups you are in.  The first number is the one
                 returned by getgid(), and the subsequent ones by
                 getgroups(), one of which may be the same as the
                 first number.
    
                 However, a value assigned to `$(' must be a single
                 number used to set the real gid.  So the value given
                 by `$(' should not be assigned back to `$(' without
                 being forced numeric, such as by adding zero.
    
                 (Mnemonic: parentheses are used to group things.
                 The real gid is the group you left, if you're
                 running setgid.)
    
         $EFFECTIVE_GROUP_ID
    
         $EGID
    
         $)      The effective gid of this process.  If you are on a
                 machine that supports membership in multiple groups
                 simultaneously, gives a space separated list of
                 groups you are in.  The first number is the one
                 returned by getegid(), and the subsequent ones by
                 getgroups(), one of which may be the same as the
                 first number.
    
                 Similarly, a value assigned to `$)' must also be a
                 space-separated list of numbers.  The first number
                 sets the effective gid, and the rest (if any) are
                 passed to setgroups().  To get the effect of an
                 empty list for setgroups(), just repeat the new
                 effective gid; that is, to force an effective gid of
                 5 and an effectively empty setgroups() list, say `
                 $) = "5 5" '.
    
                 (Mnemonic: parentheses are used to group things.
                 The effective gid is the group that's right for you,
                 if you're running setgid.)
    
                 `$<', `$>', `$(' and `$)' can be set only on
                 machines that support the corresponding
                 set[re][ug]id() routine.  `$(' and `$)' can be
                 swapped only on machines supporting setregid().
    
         $PROGRAM_NAME
    
         $0      Contains the name of the program being executed.  On
                 some operating systems assigning to `$0' modifies
                 the argument area that the ps program sees.  This is
                 more useful as a way of indicating the current
                 program state than it is for hiding the program
                 you're running.  (Mnemonic: same as sh and ksh.)
    
    
         $[      The index of the first element in an array, and of
                 the first character in a substring.  Default is 0,
                 but you could theoretically set it to 1 to make Perl
                 behave more like awk (or Fortran) when subscripting
                 and when evaluating the index() and substr()
                 functions.  (Mnemonic: [ begins subscripts.)
    
                 As of release 5 of Perl, assignment to `$[' is
                 treated as a compiler directive, and cannot
                 influence the behavior of any other file.  Its use
                 is highly discouraged.
    
         $]      The version + patchlevel / 1000 of the Perl
                 interpreter.  This variable can be used to determine
                 whether the Perl interpreter executing a script is
                 in the right range of versions.  (Mnemonic: Is this
                 version of perl in the right bracket?)  Example:
    
                     warn "No checksumming!\n" if $] < 3.019;
    
                 See also the documentation of `use VERSION' and
                 `require VERSION' for a convenient way to fail if
                 the running Perl interpreter is too old.
    
                 The use of this variable is deprecated.  The
                 floating point representation can sometimes lead to
                 inaccurate numeric comparisons.  See `$^V' for a
                 more modern representation of the Perl version that
                 allows accurate string comparisons.
    
         $COMPILING
    
         $^C     The current value of the flag associated with the -c
                 switch.  Mainly of use with -MO=... to allow code to
                 alter its behavior when being compiled, such as for
                 example to AUTOLOAD at compile time rather than
                 normal, deferred loading.  See the perlcc manpage.
                 Setting `$^C = 1' is similar to calling
                 `B::minus_c'.
    
         $DEBUGGING
    
         $^D     The current value of the debugging flags.
                 (Mnemonic: value of -D switch.)
    
         $SYSTEM_FD_MAX
    
         $^F     The maximum system file descriptor, ordinarily 2.
                 System file descriptors are passed to exec()ed
                 processes, while higher file descriptors are not.
                 Also, during an open(), system file descriptors are
                 preserved even if the open() fails.  (Ordinary file
                 descriptors are closed before the open() is
                 attempted.)  The close-on-exec status of a file
                 descriptor will be decided according to the value of
                 `$^F' when the corresponding file, pipe, or socket
                 was opened, not the time of the exec().
    
         $^H     WARNING: This variable is strictly for internal use
                 only.  Its availability, behavior, and contents are
                 subject to change without notice.
    
                 This variable contains compile-time hints for the
                 Perl interpreter.  At the end of compilation of a
                 BLOCK the value of this variable is restored to the
                 value when the interpreter started to compile the
                 BLOCK.
    
                 When perl begins to parse any block construct that
                 provides a lexical scope (e.g., eval body, required
                 file, subroutine body, loop body, or conditional
                 block), the existing value of $^H is saved, but its
                 value is left unchanged.  When the compilation of
                 the block is completed, it regains the saved value.
                 Between the points where its value is saved and
                 restored, code that executes within BEGIN blocks is
                 free to change the value of $^H.
    
                 This behavior provides the semantic of lexical
                 scoping, and is used in, for instance, the `use
                 strict' pragma.
    
                 The contents should be an integer; different bits of
                 it are used for different pragmatic flags.  Here's
                 an example:
    
                     sub add_100 { $^H |= 0x100 }
    
                     sub foo {
                         BEGIN { add_100() }
                         bar->baz($boon);
                     }
    
                 Consider what happens during execution of the BEGIN
                 block.  At this point the BEGIN block has already
                 been compiled, but the body of foo() is still being
                 compiled.  The new value of $^H will therefore be
                 visible only while the body of foo() is being
                 compiled.
    
                 Substitution of the above BEGIN block with:
    
                     BEGIN { require strict; strict->import('vars') }
    
                 demonstrates how `use strict 'vars'' is implemented.
                 Here's a conditional version of the same lexical
                 pragma:
    
                     BEGIN { require strict; strict->import('vars') if $condition }
    
    
         %^H     WARNING: This variable is strictly for internal use
                 only.  Its availability, behavior, and contents are
                 subject to change without notice.
    
                 The %^H hash provides the same scoping semantic as
                 $^H.  This makes it useful for implementation of
                 lexically scoped pragmas.
    
         $INPLACE_EDIT
    
         $^I     The current value of the inplace-edit extension.
                 Use `undef' to disable inplace editing.  (Mnemonic:
                 value of -i switch.)
    
         $^M     By default, running out of memory is an untrappable,
                 fatal error.  However, if suitably built, Perl can
                 use the contents of `$^M' as an emergency memory
                 pool after die()ing.  Suppose that your Perl were
                 compiled with -DPERL_EMERGENCY_SBRK and used Perl's
                 malloc.  Then
    
                     $^M = 'a' x (1 << 16);
    
                 would allocate a 64K buffer for use when in
                 emergency.  See the INSTALL file in the Perl
                 distribution for information on how to enable this
                 option.  To discourage casual use of this advanced
                 feature, there is no the English manpage long name
                 for this variable.
    
         $OSNAME
    
         $^O     The name of the operating system under which this
                 copy of Perl was built, as determined during the
                 configuration process.  The value is identical to
                 `$Config{'osname'}'.  See also the Config manpage
                 and the -V command-line switch documented in the
                 perlrun manpage.
    
         $PERLDB
    
         $^P     The internal variable for debugging support.  The
                 meanings of the various bits are subject to change,
                 but currently indicate:
    
                 0x01  Debug subroutine enter/exit.
    
                 0x02  Line-by-line debugging.
    
                 0x04  Switch off optimizations.
    
                 0x08  Preserve more data for future interactive
                       inspections.
    
                 0x10  Keep info about source lines on which a
                       subroutine is defined.
    
                 0x20  Start with single-step on.
    
                 0x40  Use subroutine address instead of name when
                       reporting.
    
                 0x80  Report `goto &subroutine' as well.
    
                 0x100 Provide informative "file" names for evals
                       based on the place they were compiled.
    
                 0x200 Provide informative names to anonymous
                       subroutines based on the place they were
                       compiled.
    
                 Some bits may be relevant at compile-time only, some
                 at run-time only.  This is a new mechanism and the
                 details may change.
    
         $LAST_REGEXP_CODE_RESULT
    
         $^R     The result of evaluation of the last successful `(?{
                 code })' regular expression assertion (see the
                 perlre manpage).  May be written to.
    
         $EXCEPTIONS_BEING_CAUGHT
    
         $^S     Current state of the interpreter.  Undefined if
                 parsing of the current module/eval is not finished
                 (may happen in $SIG{__DIE__} and $SIG{__WARN__}
                 handlers).  True if inside an eval(), otherwise
                 false.
    
         $BASETIME
    
         $^T     The time at which the program began running, in
                 seconds since the epoch (beginning of 1970).  The
                 values returned by the -M, -A, and -C filetests are
                 based on this value.
    
    
         $PERL_VERSION
    
         $^V     The revision, version, and subversion of the Perl
                 interpreter, represented as a string composed of
                 characters with those ordinals.  Thus in Perl v5.6.0
                 it equals `chr(5) . chr(6) . chr(0)' and will return
                 true for `$^V eq v5.6.0'.  Note that the characters
                 in this string value can potentially be in Unicode
                 range.
    
                 This can be used to determine whether the Perl
                 interpreter executing a script is in the right range
                 of versions.  (Mnemonic: use ^V for Version
                 Control.)  Example:
    
                     warn "No "our" declarations!\n" if $^V and $^V lt v5.6.0;
    
                 See the documentation of `use VERSION' and `require
                 VERSION' for a convenient way to fail if the running
                 Perl interpreter is too old.
    
                 See also `$]' for an older representation of the
                 Perl version.
    
         $WARNING
    
         $^W     The current value of the warning switch, initially
                 true if -w was used, false otherwise, but directly
                 modifiable.  (Mnemonic:  related to the -w switch.)
                 See also the warnings manpage.
    
         ${^WARNING_BITS}
                 The current set of warning checks enabled by the
                 `use warnings' pragma.  See the documentation of
                 `warnings' for more details.
    
         ${^WIDE_SYSTEM_CALLS}
                 Global flag that enables system calls made by Perl
                 to use wide character APIs native to the system, if
                 available.  This is currently only implemented on
                 the Windows platform.
    
                 This can also be enabled from the command line using
                 the `-C' switch.
    
                 The initial value is typically `0' for compatibility
                 with Perl versions earlier than 5.6, but may be
                 automatically set to `1' by Perl if the system
                 provides a user-settable default (e.g.,
                 `$ENV{LC_CTYPE}').
    
                 The `bytes' pragma always overrides the effect of
                 this flag in the current lexical scope.  See the
                 bytes manpage.
    
         $EXECUTABLE_NAME
    
         $^X     The name that the Perl binary itself was executed
                 as, from C's `argv[0]'.  This may not be a full
                 pathname, nor even necessarily in your path.
    
         $ARGV   contains the name of the current file when reading
                 from <>.
    
         @ARGV   The array @ARGV contains the command-line arguments
                 intended for the script.  `$#ARGV' is generally the
                 number of arguments minus one, because `$ARGV[0]' is
                 the first argument, not the program's command name
                 itself.  See `$0' for the command name.
    
         @INC    The array @INC contains the list of places that the
                 `do EXPR', `require', or `use' constructs look for
                 their library files.  It initially consists of the
                 arguments to any -I command-line switches, followed
                 by the default Perl library, probably
                 /usr/local/lib/perl, followed by ".", to represent
                 the current directory.  If you need to modify this
                 at runtime, you should use the `use lib' pragma to
                 get the machine-dependent library properly loaded
                 also:
    
                     use lib '/mypath/libdir/';
                     use SomeMod;
    
    
         @_      Within a subroutine the array @_ contains the
                 parameters passed to that subroutine.  See the
                 perlsub manpage.
    
         %INC    The hash %INC contains entries for each filename
                 included via the `do', `require', or `use'
                 operators.  The key is the filename you specified
                 (with module names converted to pathnames), and the
                 value is the location of the file found.  The
                 `require' operator uses this hash to determine
                 whether a particular file has already been included.
    
         %ENV
    
         $ENV{expr}
                 The hash %ENV contains your current environment.
                 Setting a value in `ENV' changes the environment for
                 any child processes you subsequently fork() off.
    
         %SIG
    
         $SIG{expr}
                 The hash %SIG contains signal handlers for signals.
                 For example:
    
                     sub handler {       # 1st argument is signal name
                         my($sig) = @_;
                         print "Caught a SIG$sig--shutting down\n";
                         close(LOG);
                         exit(0);
                     }
    
                     $SIG{'INT'}  = \&handler;
                     $SIG{'QUIT'} = \&handler;
                     ...
                     $SIG{'INT'}  = 'DEFAULT';   # restore default action
                     $SIG{'QUIT'} = 'IGNORE';    # ignore SIGQUIT
    
                 Using a value of `'IGNORE'' usually has the effect
                 of ignoring the signal, except for the `CHLD'
                 signal.  See the perlipc manpage for more about this
                 special case.
    
                 Here are some other examples:
    
                     $SIG{"PIPE"} = "Plumber";   # assumes main::Plumber (not recommended)
                     $SIG{"PIPE"} = \&Plumber;   # just fine; assume current Plumber
                     $SIG{"PIPE"} = *Plumber;    # somewhat esoteric
                     $SIG{"PIPE"} = Plumber();   # oops, what did Plumber() return??
    
                 Be sure not to use a bareword as the name of a
                 signal handler, lest you inadvertently call it.
    
                 If your system has the sigaction() function then
                 signal handlers are installed using it.  This means
                 you get reliable signal handling.  If your system
                 has the SA_RESTART flag it is used when signals
                 handlers are installed.  This means that system
                 calls for which restarting is supported continue
                 rather than returning when a signal arrives.  If you
                 want your system calls to be interrupted by signal
                 delivery then do something like this:
    
                     use POSIX ':signal_h';
    
                     my $alarm = 0;
                     sigaction SIGALRM, new POSIX::SigAction sub { $alarm = 1 }
                         or die "Error setting SIGALRM handler: $!\n";
    
                 See the POSIX manpage.
    
                 Certain internal hooks can be also set using the
                 %SIG hash.  The routine indicated by
                 `$SIG{__WARN__}' is called when a warning message is
                 about to be printed.  The warning message is passed
                 as the first argument.  The presence of a __WARN__
                 hook causes the ordinary printing of warnings to
                 STDERR to be suppressed.  You can use this to save
                 warnings in a variable, or turn warnings into fatal
                 errors, like this:
    
                     local $SIG{__WARN__} = sub { die $_[0] };
                     eval $proggie;
    
                 The routine indicated by `$SIG{__DIE__}' is called
                 when a fatal exception is about to be thrown.  The
                 error message is passed as the first argument.  When
                 a __DIE__ hook routine returns, the exception
                 processing continues as it would have in the absence
                 of the hook, unless the hook routine itself exits
                 via a `goto', a loop exit, or a die().  The
                 `__DIE__' handler is explicitly disabled during the
                 call, so that you can die from a `__DIE__' handler.
                 Similarly for `__WARN__'.
    
                 Due to an implementation glitch, the `$SIG{__DIE__}'
                 hook is called even inside an eval().  Do not use
                 this to rewrite a pending exception in `$@', or as a
                 bizarre substitute for overriding
                 CORE::GLOBAL:\fIs0:die().  This strange action at a
                 distance may be fixed in a future release so that
                 `$SIG{__DIE__}' is only called if your program is
                 about to exit, as was the original intent.  Any
                 other use is deprecated.
    
                 `__DIE__'/`__WARN__' handlers are very special in
                 one respect:  they may be called to report
                 (probable) errors found by the parser.  In such a
                 case the parser may be in inconsistent state, so any
                 attempt to evaluate Perl code from such a handler
                 will probably result in a segfault.  This means that
                 warnings or errors that result from parsing Perl
                 should be used with extreme caution, like this:
    
                     require Carp if defined $^S;
                     Carp::confess("Something wrong") if defined &Carp::confess;
                     die "Something wrong, but could not load Carp to give backtrace...
                          To see backtrace try starting Perl with -MCarp switch";
    
                 Here the first line will load Carp unless it is the
                 parser who called the handler.  The second line will
                 print backtrace and die if Carp was available.  The
                 third line will be executed only if Carp was not
                 available.
    
                 See the die entry in the perlfunc manpage, the warn
                 entry in the perlfunc manpage, the eval entry in the
                 perlfunc manpage, and the warnings manpage for
                 additional information.
    
         Error Indicators
    
         The variables `$@', `$!', `$^E', and `$?' contain
         information about different types of error conditions that
         may appear during execution of a Perl program.  The
         variables are shown ordered by the "distance" between the
         subsystem which reported the error and the Perl process.
         They correspond to errors detected by the Perl interpreter,
         C library, operating system, or an external program,
         respectively.
    
         To illustrate the differences between these variables,
         consider the following Perl expression, which uses a
         single-quoted string:
    
             eval q{
                 open PIPE, "/cdrom/install |";
                 @res = <PIPE>;
                 close PIPE or die "bad pipe: $?, $!";
             };
    
         After execution of this statement all 4 variables may have
         been set.
    
         `$@' is set if the string to be `eval'-ed did not compile
         (this may happen if `open' or `close' were imported with bad
         prototypes), or if Perl code executed during evaluation
         die()d .  In these cases the value of $@ is the compile
         error, or the argument to `die' (which will interpolate `$!'
         and `$?'!).  (See also the Fatal manpage, though.)
    
         When the eval() expression above is executed, open(),
         `<PIPE>', and `close' are translated to calls in the C run-
         time library and thence to the operating system kernel.
         `$!' is set to the C library's `errno' if one of these calls
         fails.
    
         Under a few operating systems, `$^E' may contain a more
         verbose error indicator, such as in this case, "CDROM tray
         not closed."  Systems that do not support extended error
         messages leave `$^E' the same as `$!'.
    
         Finally, `$?' may be set to non-0 value if the external
         program /cdrom/install fails.  The upper eight bits reflect
         specific error conditions encountered by the program (the
         program's exit() value).   The lower eight bits reflect mode
         of failure, like signal death and core dump information  See
         wait(2) for details.  In contrast to `$!' and `$^E', which
         are set only if error condition is detected, the variable
         `$?' is set on each `wait' or pipe `close', overwriting the
         old value.  This is more like `$@', which on every eval() is
         always set on failure and cleared on success.
    
         For more details, see the individual descriptions at `$@',
         `$!', `$^E', and `$?'.
    
         Technical Note on the Syntax of Variable Names
    
         Variable names in Perl can have several formats.  Usually,
         they must begin with a letter or underscore, in which case
         they can be arbitrarily long (up to an internal limit of 251
         characters) and may contain letters, digits, underscores, or
         the special sequence `::' or `''.  In this case, the part
         before the last `::' or `'' is taken to be a package
         qualifier; see the perlmod manpage.
    
         Perl variable names may also be a sequence of digits or a
         single punctuation or control character.  These names are
         all reserved for special uses by Perl; for example, the
         all-digits names are used to hold data captured by
         backreferences after a regular expression match.  Perl has a
         special syntax for the single-control-character names: It
         understands `^X' (caret `X') to mean the control-`X'
         character.  For example, the notation `$^W' (dollar-sign
         caret `W') is the scalar variable whose name is the single
         character control-`W'.  This is better than typing a literal
         control-`W' into your program.
    
         Finally, new in Perl 5.6, Perl variable names may be
         alphanumeric strings that begin with control characters (or
         better yet, a caret).  These variables must be written in
         the form `${^Foo}'; the braces are not optional.  `${^Foo}'
         denotes the scalar variable whose name is a control-`F'
         followed by two `o''s.  These variables are reserved for
         future special uses by Perl, except for the ones that begin
         with `^_' (control-underscore or caret-underscore).  No
         control-character name that begins with `^_' will acquire a
         special meaning in any future version of Perl; such names
         may therefore be used safely in programs.  `$^_' itself,
         however, is reserved.
    
         Perl identifiers that begin with digits, control characters,
         or punctuation characters are exempt from the effects of the
         `package' declaration and are always forced to be in package
         `main'.  A few other names are also exempt:
    
    
                 ENV             STDIN
                 INC             STDOUT
                 ARGV            STDERR
                 ARGVOUT
                 SIG
    
         In particular, the new special `${^_XYZ}' variables are
         always taken to be in package `main', regardless of any
         `package' declarations presently in scope.
    
    
    

    BUGS

         Due to an unfortunate accident of Perl's implementation,
         `use English' imposes a considerable performance penalty on
         all regular expression matches in a program, regardless of
         whether they occur in the scope of `use English'.  For that
         reason, saying `use English' in libraries is strongly
         discouraged.  See the Devel::SawAmpersand module
         documentation from CPAN
         (http://www.perl.com/CPAN/modules/by-module/Devel/) for more
         information.
    
         Having to even think about the `$^S' variable in your
         exception handlers is simply wrong.  `$SIG{__DIE__}' as
         currently implemented invites grievous and difficult to
         track down errors.  Avoid it and use an `END{}' or
         CORE::GLOBAL::die override instead.
    
    
    
    


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