Web Standards Programmer's Reference: HTML, CSS, JavaScript®, Perl, Python®, and PHP

D.4. Standard Variables

The following tables detail the various standard variables in the Perl language.

D.4.1. Global Variables

Variable	Use
$_	The default input and pattern-searching space.
$.	The current input line number of the last filehandle read.
$/	The input record separator (newline is the default).
$,	The output field separator for the print operator.
$"	The separator joining elements of arrays interpolated in strings.
$\	The output record separator for the print operator.
$?	The status returned by the last `. . .` command, pipe close, or system operator.
$]	The Perl version number.
$;	The subscript separator for multidimensional array emulation (default is \034).
$!	In a numeric context, is the current value of errno. In a string context, is the corresponding error string.
$@	The Perl error message from the last eval or do command.
$:	The set of characters after which a string may be broken to fill continuation fields in a format.
$0	The name of the file containing the Perl script being executed.
$$	The process ID of the currently executing Perl program.
$<	The real user ID of the current process.
$>	The effective user ID of the current process.
$(	The real group ID of the current process.
$)	The effective group ID of the current process.
$^A	The accumulator for formline and write operations.
$^D	The debug flags; passed to Perl using the -D command line argument.
$^F	The highest system file descriptor.
$^I	In-place edit extension, passed to Perl using the -i command line argument.
$^L	Formfeed character used in ...