app01lev1sec2.html

A.2. Special Variables

Table A.2. Filehandles
Variable What It Does
$| If nonzero, forces buffer flush after every write and print on the currently selected filehandle
$% Current page number of currently selected filehandle
$= Current page length of currently selected filehandle
$– Number of lines left on the page for currently selected filehandle
$~ Name of current report format for currently selected filehandle
$^ Name of current top-of-page format for currently selected filehandle

Table A.2. Filehandles
Variable	What It Does
$\|	If nonzero, forces buffer flush after every write and print on the currently selected filehandle
$%	Current page number of currently selected filehandle
$=	Current page length of currently selected filehandle
$–	Number of lines left on the page for currently selected filehandle
$~	Name of current report format for currently selected filehandle
$^	Name of current top-of-page format for currently selected filehandle

Table A.3. Local to Block
Variable What It Does
$1.. $9 Contains remembered subpatterns that reference a corresponding set of parentheses (same as \1..\9)
$ & The string matched by the last pattern match (like sed editor)
$' The string preceding what was matched in the last pattern match
$' The string that follows whatever was matched by the last pattern match
$+ The last pattern matched by the last search pattern

Table A.3. Local to Block
Variable	What It Does
$1.. $9	Contains remembered subpatterns that reference a corresponding set of parentheses (same as \1..\9)
$ &	The string matched by the last pattern match (like sed editor)
$'	The string preceding what was matched in the last pattern match
$'	The string that follows whatever was matched by the last pattern match
$+	The last pattern matched by the last search pattern

Example A.1.

$str="old and restless"; print "$&\n" if $str =~ /and/; print "$'\n" if $str =~ /and/; print "$'\n" if $str =~ /and/; print "\nold string is: $str\n"; $str=~s/(old) and (restless)/$2 and $1/; print "new string is: $str\n"; print "\nlast pattern matched: $+\n"; (Output) and old restless old string is: old and restless new string is: restless and old last pattern matched is: restless

Table A.4. Global
Variable What It Does
$_ Default input and pattern-searching space.
$. Current input line number of last filehandle that was read; must close the filehandle to reset line numbers for next filehandle.
$/ Input record separator, newline by default. (Like RS in awk.)
$\ Output record separator for the print function. Does not print a newline unless set: $\="\n"
$, Output field separator for the print function. Normally delimiter is not printed between comma-separated strings unless set: S,=" ".
$" Same as $ but applies to printing arrays when in double quotes. Default is space.
$# Output format for numbers printed with the print function. (Like OMFT in awk.)
$$ The process ID number of the Perl program running this script.
$? Status returned by last pipe closed, command in backquotes, or system function.
$* Default is 0. If set to 1, does a multiline match within a string; 0 for a match within a single line.
$0 Name of this Perl script.
$[ Index of first element of an array, and first character in a substring. Default is 0.
$] The first part of the string is printed out when using perl -v for version information.
$; The subscript separator for multidimensional array emulation. Default is \034. (Like SUBSEP in awk.)
$! Yields the current value of errno (system error number) if numeric, and the corresponding system error string.
$@ Error message from the last eval, do, or require function.
$< The real uid of this process.
$> The effective uid of this process.
$( The real gid of this process.
$) The effective gid of this process.
$: The set of characters after which a string may be broken to fill continuation lines (starting with ^) in a format. Default is \n- to break on whitespace, newline, or colon.
$^A The accumulator for formline and write operations.
$^C TRUE if Perl is run in compile-only mode using command-line option -c.
$^D Perl's debug flags when -D switch is used.
$^E Operating-system-dependent error information.
$^F Maximum file descriptor passed to subprocess, usually 2.
$^H The current state of syntax checks.
$^I Current value of inplace-edit extension when -i switch is used. Use undef to disable inplace editing.
$^L Form feed character used in formats.
$^M Emergency memory pool.
$^O Name of the operating system.
$^P Internal Perl debugging flag.
$^S State of the Perl interpreter.
$^T Time of day when script started execution. Used by -A, -C, and -M test operators and can be set to any number value returned by time to perform file tests relative to the current time.
$^V The Perl version.
$^W The current value of the warning switch.
$^X The full pathname by which this Perl was invoked.
_ An underscore. The special designator for file testing when stating files.
ARGV The special filehandle array for looping over line arguments.
$ARGV The variable containing the name of the current file when reading from <ARGV>.
@ARGV The array containing command-line arguments.
DATA Special filehandle referring to anything following _ _END_ _.
@F The array into which input lines are autosplit when the -a switch is used.
@INC Array containing pathnames where require and do functions look for files that are to be included in this script.
%INC Associative array containing entries for files that have been included by calling do or require. The key is the filename and the value is its location.
%ENV Associative array containing the current environment.
@EXPORT Default symbols to be exported.
@EXPORT_OK Symbols to be exported upon request by the user.
%EXPORT_TAGS Used by Exporter.pm to collectively name sets of symbols.
%SIG Associative array used to set signal handlers.
STDERR Special filehandle for standard error.
STDIN Special filehandle for standard input.
STDOUT Special filehandle for standard output.

Variable	What It Does
$_	Default input and pattern-searching space.
$.	Current input line number of last filehandle that was read; must close the filehandle to reset line numbers for next filehandle.
$/	Input record separator, newline by default. (Like RS in awk.)
$\	Output record separator for the print function. Does not print a newline unless set: $\="\n"
$,	Output field separator for the print function. Normally delimiter is not printed between comma-separated strings unless set: S,=" ".
$"	Same as $ but applies to printing arrays when in double quotes. Default is space.
$#	Output format for numbers printed with the print function. (Like OMFT in awk.)
$$	The process ID number of the Perl program running this script.
$?	Status returned by last pipe closed, command in backquotes, or system function.
$*	Default is 0. If set to 1, does a multiline match within a string; 0 for a match within a single line.
$0	Name of this Perl script.
$[	Index of first element of an array, and first character in a substring. Default is 0.
$]	The first part of the string is printed out when using perl -v for version information.
$;	The subscript separator for multidimensional array emulation. Default is \034. (Like SUBSEP in awk.)
$!	Yields the current value of errno (system error number) if numeric, and the corresponding system error string.
$@	Error message from the last eval, do, or require function.
$<	The real uid of this process.
$>	The effective uid of this process.
$(	The real gid of this process.
$)	The effective gid of this process.
$:	The set of characters after which a string may be broken to fill continuation lines (starting with ^) in a format. Default is \n- to break on whitespace, newline, or colon.
$^A	The accumulator for formline and write operations.
$^C	TRUE if Perl is run in compile-only mode using command-line option -c.
$^D	Perl's debug flags when -D switch is used.
$^E	Operating-system-dependent error information.
$^F	Maximum file descriptor passed to subprocess, usually 2.
$^H	The current state of syntax checks.
$^I	Current value of inplace-edit extension when -i switch is used. Use undef to disable inplace editing.
$^L	Form feed character used in formats.
$^M	Emergency memory pool.
$^O	Name of the operating system.
$^P	Internal Perl debugging flag.
$^S	State of the Perl interpreter.
$^T	Time of day when script started execution. Used by -A, -C, and -M test operators and can be set to any number value returned by time to perform file tests relative to the current time.
$^V	The Perl version.
$^W	The current value of the warning switch.
$^X	The full pathname by which this Perl was invoked.
_	An underscore. The special designator for file testing when stating files.
ARGV	The special filehandle array for looping over line arguments.
$ARGV	The variable containing the name of the current file when reading from <ARGV>.
@ARGV	The array containing command-line arguments.
DATA	Special filehandle referring to anything following _ _END_ _.
@F	The array into which input lines are autosplit when the -a switch is used.
@INC	Array containing pathnames where require and do functions look for files that are to be included in this script.
%INC	Associative array containing entries for files that have been included by calling do or require. The key is the filename and the value is its location.
%ENV	Associative array containing the current environment.
@EXPORT	Default symbols to be exported.
@EXPORT_OK	Symbols to be exported upon request by the user.
%EXPORT_TAGS	Used by Exporter.pm to collectively name sets of symbols.
%SIG	Associative array used to set signal handlers.
STDERR	Special filehandle for standard error.
STDIN	Special filehandle for standard input.
STDOUT	Special filehandle for standard output.