my $regex = qr/(\d\d):(\d\d)(?::(\d\d))?/;

#             01234567890123456
my $string = "11:30 or 11:29:53";

##</code><code>##

$res = { 0  => ['11', '30', undef],
         19 => ['11', '29', '53']
       }

##</code><code>##

$res->{pos ($string)} = [$1, $2, $3] while $string = /$regex/g;

##</code><code>##

@res = $string = /$regex/g;