$^H WARNING: This variable is strictly for internal use only. Its availability, behavior, and contents are subject to change without notice

%+ Similar to @+ , the %+ hash allows

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

$INPUT_LINE_NUMBER

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

$] The revision, version, and subversion of the Perl interpreter, represented as a decimal of the form 5.XXXYYY, where XXX is the version /

$" When an array or an array slice is interpolated into a double-quoted string or a similar context such as /

@+ This array holds the offsets of the ends of the last successful submatches in the currently active dynamic scope.

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

$^W The current value of the warning switch, initially true if -w was used, false otherwise, but directly modifiable.