$^ The name of the current top-of-page format for the currently selected output channel. The default is the name of the filehandle with

$0 Contains the name of the program being executed. On some (but not all) operating systems assigning to

${^TAINT} Reflects if taint mode is on or off. 1 for on (the program was run with -T), 0 for off, -1 when only taint warnings are enabled

@ARG

$^N The text matched by the used group most-recently closed (i.e. the group with the rightmost closing parenthesis) of the last successful

$MATCH

$$ The process number of the Perl running this script. Though you can set this variable, doing so is generally discouraged, although

$INPUT_LINE_NUMBER

$b Special package variables when using sort()

${^MATCH} This is similar to $& ($MATCH