ESC[1mDESCRIPTIONESC[0m
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.
ESC[1mOPERATORSESC[0m
"=~" determines to which variable the regex is applied. In its
absence, $_
is used.