sub match_all_ways { my ($string, $regex) = @_; my $count; my $incr = qr/(?{$count++})/; $string =~ /(?:$regex)$incr(?!)/; return $count; } print match_all_ways("abcdef", qr/..*..*./); # 20 print match_all_ways("abcdef", qr/..*..*./); # undef