Does the 'o' modifier for Perl regular expressions still provide any benefit?

Question

It used to be considered beneficial to include the \'o\' modifier at the end of Perl regular expressions. The current Perl documentation does not even seem to list it, cert

Answer 1

One thing it, mystifyingly, does not do is, allow a ONCE block, at least at 5.8.8.

perl -le 'for (1..3){ print; m/${\(print( "between 1 and 2 only"), 3)}/o and print "matched" }'