Full documentation of predefined variables:perlvar
$_ - The default input and pattern-searching space
@_ - Within a subroutine the array@_ contains the parameters passed to that subroutine
$" - When an array or an array slice is interpolated into a double-quoted string or a similar context such as/.../, its elements are separated by this value
$$ - The process number of the Perl running this script
$0 - Contains the name of the program being executed
$( - The real gid of this process
$) - The effective gid of this process
$< - The real uid of this process
$> - The effective uid of this process
$; - The subscript separator for multidimensional array emulation
$a,$b - Special package variables when usingsort(), see"sort" in perlfunc
%ENV - The hash%ENV contains your current environment
$] - The revision, version, and subversion of the Perl interpreter, represented as a decimal of the form 5.XXXYYY, where XXX is the version / 1e3 and YYY is the subversion / 1e6
$^F - The maximum system file descriptor, ordinarily 2. System file descriptors are passed toexec()ed processes, while higher file descriptors are not
@F - The array@F contains the fields of each line read in when autosplit mode is turned on
@INC - The array@INC contains the list of places that thedo EXPR,require, oruse constructs look for their library files
%INC - The hash%INC contains entries for each filename included via thedo,require, oruse operators
$^I - The current value of the inplace-edit extension
@ISA - Each package contains a special array called@ISA which contains a list of that class's parent classes, if any
$^M - Perl can use the contents of$^M as an emergency memory pool afterdie()ing
$^O - The name of the operating system under which this copy of Perl was built, as determined during the configuration process
%SIG - The hash%SIG contains signal handlers for signals
$^T - The time at which the program began running, in seconds since the epoch (beginning of 1970)
$^V - The revision, version, and subversion of the Perl interpreter, represented as aversion object
${^WIN32_SLOPPY_STAT} - If this variable is set to a true value, thenstat() on Windows will not try to open the file
$^X - The name used to execute the current copy of Perl, from C'sargv[0] or (where supported)/proc/self/exe
$<digits> ($1, $2, ...) - Contains the subpattern from the corresponding set of capturing parentheses from the last successful pattern match, not counting patterns matched in nested blocks that have been exited already
@{^CAPTURE} - An array which exposes the contents of the capture buffers, if any, of the last successful pattern match, not counting patterns matched in nested blocks that have been exited already
$& - The string matched by the last successful pattern match (not counting any matches hidden within a BLOCK oreval() enclosed by the current BLOCK)
${^MATCH} - This is similar to$& ($MATCH) except that it does not incur the performance penalty associated with that variable
$` - The string preceding whatever was matched by the last successful pattern match, not counting any matches hidden within a BLOCK oreval enclosed by the current BLOCK
${^PREMATCH} - This is similar to$` ($PREMATCH) except that it does not incur the performance penalty associated with that variable
$' - The string following whatever was matched by the last successful pattern match (not counting any matches hidden within a BLOCK oreval() enclosed by the current BLOCK)
${^POSTMATCH} - This is similar to$' ($POSTMATCH) except that it does not incur the performance penalty associated with that variable
$+ - The text matched by the highest used capture group of the last successful search pattern
$^N - The text matched by the used group most-recently closed (i.e. the group with the rightmost closing parenthesis) of the last successful search pattern
@+ - This array holds the offsets of the ends of the last successful submatches in the currently active dynamic scope
%+ - Similar to@+, the%+ hash allows access to the named capture buffers, should they exist, in the last successful match in the currently active dynamic scope
@- -$-[0] is the offset of the start of the last successful match
%- - Similar to%+, this variable allows access to the named capture groups in the last successful match in the currently active dynamic scope
$^R - The result of evaluation of the last successful(?{ code }) regular expression assertion (seeperlre)
${^RE_COMPILE_RECURSION_LIMIT} - The current value giving the maximum number of open but unclosed parenthetical groups there may be at any point during a regular expression compilation
${^RE_DEBUG_FLAGS} - The current value of the regex debugging flags
${^RE_TRIE_MAXBUF} - Controls how certain regex optimisations are applied and how much memory they utilize
$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 - The special filehandle that iterates over command-line filenames in@ARGV
ARGVOUT - The special filehandle that points to the currently open output file when doing edit-in-place processing with-i
$, - The output field separator for the print operator
$. - Current line number for the last filehandle accessed
$/ - The input record separator, newline by default
$\ - The output record separator for the print operator
$| - If set to nonzero, forces a flush right away and after every write or print on the currently selected output channel
${^LAST_FH} - This read-only variable contains a reference to the last-read filehandle
$^A - The current value of thewrite() accumulator forformat() lines
$^L - What formats output as a form feed
$% - The current page number of the currently selected output channel
$- - The number of lines left on the page of the currently selected output channel
$: - The current set of characters after which a string may be broken to fill continuation fields (starting with^) in a format
$= - The current page length (printable lines) of the currently selected output channel
$^ - The name of the current top-of-page format for the currently selected output channel
$~ - The name of the current report format for the currently selected output channel
${^CHILD_ERROR_NATIVE} - The native status returned by the last pipe close, backtick (``) command, successful call towait() orwaitpid(), or from thesystem() operator
$^E - Error information specific to the current operating system
$^S - Current state of the interpreter
$^W - The current value of the warning switch, initially true if-w was used, false otherwise, but directly modifiable
${^WARNING_BITS} - The current set of warning checks enabled by theuse warnings pragma
$! - When referenced,$! retrieves the current value of the Cerrno integer variable
%! - Each element of%! has a true value only if$! is set to that value
$? - The status returned by the last pipe close, backtick (``) command, successful call towait() orwaitpid(), or from thesystem() operator
$@ - The Perl error from the lasteval operator, i.e. the last exception that was caught
$^C - The current value of the flag associated with the-c switch
$^D - The current value of the debugging flags
${^ENCODING} - It used to hold theobject reference to theEncode object that was used to convert the source code to Unicode
${^GLOBAL_PHASE} - The current phase of the perl interpreter
$^H - This variable contains compile-time hints for the Perl interpreter
%^H - The%^H hash provides the same scoping semantic as$^H
$^P - The internal variable for debugging support
${^TAINT} - Reflects if taint mode is on or off
${^SAFE_LOCALES} - Reflects if safe locale operations are available to this perl (when the value is 1) or not (the value is 0)
${^UNICODE} - Reflects certain Unicode settings of Perl
${^UTF8CACHE} - This variable controls the state of the internal UTF-8 offset caching code
${^UTF8LOCALE} - This variable indicates whether a UTF-8 locale was detected by perl at startup
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