$ perldoc perlhist ... Perl 1 introduced Perl to the world, and changed /\(...\|...\)/ to /(...|...)/. \(Dan Faigin still hasn't forgiven me. :−\)
It turns out that you use the metacharacters much more frequently than you do the literal characters, so it made sense to change Perl so that /(.*)/ defined a substring that could be referenced later, while /\(.*\)/ matched a sequence inside literal parentheses.
This change broke all of Dan Faigin’s scripts. I think he’s forgiven me by now, even if he won’t admit it.