perlrerefNAME perlreref - Perl Regular Expressions Reference DESCRIPTION This is a quick reference to Perl's regular expressions. For full information see perlre and perlop, as well as the "SEE ALSO" section in this document. OPERATORS =~ determines to which variable the regex is applied. In its absence, $_ is used. $var =~ /foo/; !~ determines to which variable the regex is applied, and negates the result
