http://www.perlmonks.org?node_id=1012758


in reply to Re: Detecting if a string is a regular expression
in thread Detecting if a string is a regular expression

... any $string can be used as a valid regex like in m/$string/ ...

... and you don't even need the  m// or  qr// incantation. The  =~ binding operator can do the trick:

>perl -wMstrict -le "my $s = 'abc'; ;; print 'match' if 'xabcx' =~ $s; print 'match' if 'xabcx' =~ 'abc'; " match match