Perl (5.18, at least) does let you (ab)use named groups to provide match-part identification.

Given `(?<g1>Sat)urday|(?<g2>Sun)day`, and a successful match, either `$+{g1}` or `$+{g2}` will hold the relevant subpart.

Quickie demo script:

    my $re = "(?<g1>Sat)urday|(?<g2>Sun)day";
    foreach my $d (qw(Friday Sunday Thursday Saturday)) {
        my $out = '<default>';
        if ($d =~ /$re/) {
            if ($+{g1}) { $out = 'Saturday' }
            elsif ($+{g2}) { $out = 'Sunday' }
        }
        print "$d routes to $out\n";
    }