http://www.perlmonks.org?node_id=1225323


in reply to Where can I find more examples of use of Special Backtracking Control Verbs?

I usually use '(*FAIL)' with '(?{})' to generate all possible substrings of the string, or in similar cases. E.g.
my $string = <>; my %substrings; $string =~ /(.+)(?{ $substrings{ $1 } = 1 })(*FAIL)/;
E.g. to calculate some statistics:
/ (\b\d+\b) .*? (\b\d+\b) (?{ $count += $1 > $2 }) (*FAIL) /x;
But have no experience of using PRUNE, SKIP and others :)