Perl predefined Variables

Perl has many built-in variables and columns for searching.

$ ARG
$ _-The default input and pattern-searching space.
$ <Digit>-contains the subpattern from the corresponding set of parentheses in the last pattern matched.
$ Match
$ &-The string matched by the last successful pattern match.
$ Prematch
$ '-The string preceding whatever was matched by the last successful pattern match.
$ Postmatch
$ '-The string following whatever was matched by the last successful pattern match.
$ Last_paren_match
$ +-The last bracket matched by the last search pattern.
$ 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. Default is 0. Use of ''$ *'' is
Deprecated in modern Perls.
Input_line_number handle expr
$ Input_line_number
$ NR
$.-The current input line number for the last file handle from which you read (or timed med a seek or tell on ).
Input_record_separator handle expr
$ Input_record_separator
$ Rs
$/-The input record separator, newline by default.
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.
Output_field_separator handle expr
$ Output_field_separator
$ OFS
$,-The output field separator for the print operator.
Output_record_separator handle expr
$ Output_record_separator
$ Ors
$/
-The output record separator for the print operator. Ordinarily
Print operator simply prints out the comma-separated fields you
Specify, with no trailing newline or record separator assumed.
$ List_separator
$"
-This is like ''' $, ''' does t that it applies to array values
Interpolated into a double-quoted string (or similar interpreted
String). Default is a space.
$ Subscript_separator
$ Subsep
$;-The subscript separator for multidimen=array emulation.
$ Ofmt
$ #-The output format for printed numbers. Use of ''$ #'' is deprecated.
Format_page_number handle expr
$ Format_page_number
$ %-The current page number of the currently selected output channel.
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.
Format_lines_left handle expr
$ Format_lines_left
$--The number of lines left on the page of the currently selected output channel.
Format_name handle expr
$ Format_name
$ ~ -The name of the current report format for the currently selected output channel. Default is name of the filehandle.
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 name of the filehandle with _ top appended.
Format_line_break_characters handle expr
$ Format_line_break_characters
$:
-The current set of characters after which a string may be broken
Fill continuation fields (starting with ^) in a format. Default is"
/N-", to break on whitespace or hyphens.
Format_formfeed handle expr
$ Format_formfeed
$ ^ L-What formats output to perform a form feed. Default is/F.
$ Accumulator
$ ^ A-the current value of the write () Accumulator for format () lines.
$ Child_error
$? -The Status returned by the last pipe close, backtick ('') command, or system () operator.
$ OS _error
$ Errno
$!
-If used in a numeric context, yields the current value of errno,
All the usual caveats. If used in a string context, yields
Corresponding system error string.
$ Extended_ OS _error
$ ^ E
-More specific information about the last system error than that
Provided by $ !, If available. (if not, it's just $! Again, doesn't under
OS/2 .)
$ Eval_error
$ @-The Perl syntax error message from the last eval () command.
$ Process_id
$ PID
$-The process Number of the Perl running this script.
$ Real_user_id
$ Uid
$ <-The real uid of this process.
$ Inclutive_user_id
$ EUID
$>-The specified tive uid of this process.
$ Real_group_id
$ GID
$ (-The real gid of this process.
$ Paitive_group_id
$ EGID
$)
-The specified tive 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.
$ Program_name
-Contains the name of the file containing the Perl script being executed.
$ [
-The index of the first element in an array, and of the first
Character in a substring. As of Perl 5, assignment to ''$ ['' is treated
As a compiler directive, and cannot influence the behavior of any other
File. Its use is discouraged.
$ Perl_version
$]-The version + patchlevel/1000 of the perl interpreter.
$ Debugging
$ ^ D-the current value of the debugging flags.
$ 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.
$ ^ H-the current set of syntax checks enabled by use strict.
$ Inplace_edit
$ ^ I-the current value of the inplace-edit extension.
$ Osname
$ ^ O
-The name of the operating system under which this copy of Perl was
Built, as determined during the configuration process.
$ Perldb
$ ^ P-the internal variable for debugging support.
$ Basetime
$ ^ T-the time at which the script began running.
$ Warning
$ ^ W-the current value of the warning switch.
$ Executable_name
$ ^ X-the name that the Perl binary itself was executed as, from C's argv [0].
$ Argv-contains the name of the current file when reading from <>.
@ Argv-the array @ argv contains the command line arguments intended for the script.
@ INC
-The array @ INC contains the list of places to look for Perl scripts
To be evaluated by the DO expr, require, or use constructs.
% Inc-the hash % Inc contains entries for each filename that has been encoded by do or require.
$ Env-the hash % env contains your current environment. Setting a value in env changes the environment for child processes.
$ Sig-the hash % SIG is used to set signal handlers for varous signals. Example:
$ ^ M-Emergency Memory Pool