Lazyweb, why doesn't this regexp match in Perl 5.32.1, 5.34.3 or 5.18.2 but does in PHP and JS: perl -le 'print 0 + ("ABCDE" =~ m/ABCF|BCDE|C(G)/);' Changing nearly any character, including the C before the G, or removing the parens, makes it match.