PERL VARIABLES

Special Variables	Names
$_	$ARG
@_	@ARG
$"	$LIST_SEPARATOR
$;	$SUBSCRIPT_SEPARATOR or $SUBSEP
$&	$MATCH
$`	$PREMATCH
$'	$POSTMATCH
$+	$LAST_PAREN_MATCH
$.	$INPUT_LINE_NUMBER or $NR
$/	$INPUT_RECORD_SEPARATOR or $RS
$|	$OUTPUT_AUTOFLUSH
$,	$OUTPUT_FIELD_SEPARATOR or $OFS
$\	$OUTPUT_RECORD_SEPARATOR or $ORS
$%	$FORMAT_PAGE_NUMBER
$=	$FORMAT_LINES_PER_PAGE
$_	$FORMAT_LINES_LEFT
$~	$FORMAT_NAME
$^	$FORMAT_TOP_NAME
$:	$FORMAT_LINE_BREAK_CHARACTERS
$^L	$FORMAT_FORMFEED
$?	$CHILD_ERROR
$!	$OS_ERROR or $ERRNO
$@	$EVAL_ERROR
$$	$PROCESS_ID or $PID
$<	$REAL_USER_ID or $UID
$>	$EFFECTIVE_USER_ID or $EUID
$(	$REAL_GROUP_ID or $GID
$)	$EFFECTIVE_GROUP_ID or $EGID
$0	$PROGRAM_NAME
$]	$PERL_VERSION
$^A	$ACCUMULATOR
$^D	$DEBUGGING
$^F	$SYSTEM_FD_MAX
$^I	$INPLACE_EDIT
$^P	$PERLDB
$^T	$BASETIME
$^W	$WARNING
$^X	$EXECUTABLE_NAME

Variable	Description
$_$ARG	This is the default variable which stores the current values.
$0 or $PROGRAM_NAME	Stores the file name of the Perl script.
$/	The input record separator, this has a default value of ‘n’ which is newline character
$.	Holds the current line number of the file that is being read
$,	Output field separator, this is mainly used by print() statement. By default value of this is set to 0, we can change the value of this variable.
$	Output record separator, the value of this variable will be empty; we can assign any value to this, which will be used by print() statement while printing the output.
$#	This variable is used for output format while printing numbers.
$%$FORMAT_PAGE_NUMBER	Will hold the current page number of the file read.
$=$FORMAT_LINES_PER_PAGE	Will Hold the current page length of the file read.
$-$FORMAT_LINES_LEFT	Holds the value of the number of lines left to print from the page.
$~$FORMAT_NAME	Format Name: Holds the format of the currently selected output by default the file handle name.
$^$FORMAT_TOP_NAME	Holds the value of the heading format of the file handler, by default value will be _TOP followed by file handle name.
$|$OUTPUT_AUTOFLUSH	Default is zero; this is used to flush the output buffer after every write() or print().
$$	Will hold the running process number of Perl interpreter.
$?	Status code : Pipe and system call. Return status of the command executed.
$&$MATCH	Used in regular expressions, this will hold a string of the last successful pattern match.
$`$PREMATCH	Used in regular expressions, this will hold string preceded by last successful pattern match.
$’$POSTMATCH	Used in regular expressions, this will hold a string that followed by the last successful pattern match.
$+$LAST_PAREN_MATCH	Holds the string of the last bracket that is matched by the last pattern search.
$<digit>	$1, $2, $3 …. Holds the values of the pattern matched in order.
$[	First index: Array, substring.
$]	Version of Perl.
$”	Separator used for list elements, by default value is a white space.
$;	Subscript separator used in multi-dimensional arrays
$!	In numeric context, prints the error number. In string context, print the error.
$@	Will hold the syntax error info, used when eval() is used.
$<	Holds the real UID (user id) of the process running the script.
$>	Holds the effective UID of the process running the script.
$(	Holds the real GID (group id) of the process running the script.
$)	Holds the effective GID of the process running the script.
$^D$DEBUGGING	Holds the current value of the debugging flags.
$^C	Holds the current value of the flag when –c command line switch is used.
$^F	Maximum system file descriptor, by default value is set to 2
$^I$INPLACE_EDIT	Holds the value of –i command line switch.
$^M	Special Memory pool, can be used when Perl script dies with out-off memory error.
$^O$OSNAME	Operating system info is stored. ‘Linux’ for Linux systems, ‘mswin32′ for Windows systems.
$^T$BASETIME	The time when the scripts running in seconds.
$^W$WARNING	The current value of the –w command line switch. Warning switch.
$ARGV	Name of the current file, when <> is used.

Array Special Variables:

Variable	Description
@INC	Holds a list of paths, where Perl library modules or scripts can be looked into while executing the current script. This @INC is used by use and require statements to look into those paths for library modules.
@ARGV	Stores the command line arguments passed.
@_	Used in subroutines, while passing the parameters to the subroutines.
@F	This is the array into which the input lines are stored when auto split –a (command line switch is used).

Hash Special Variables:

Variable	Description
%INC	File name will be the keys; values will be the path to those files. Used by do, use and require.
%ENV	System environmental variables.
%SIG	Signals handler.