for (split(/:/, $$pattern)) {
    $_ = 'S0' . $_ unless /^S/;
    $_ .= 'S0' unless /S\d+$/;
    print STDERR "pattern: $_\n";
    my @pieces = split(/[SF](\d+)/, $_);
    foreach my $count (0..$#pieces) {
        print STDERR "$count -> [$pieces[$count]] ";
    }
    print STDERR "\n";
}

##</code><code>##

pattern: S51F11S0
0 -> [] 1 -> [51] 2 -> [] 3 -> [11] 4 -> [] 5 -> [0]

##</code><code>##

pattern: S51F11S0
0 -> [51] 1 -> [11] 2 -> [0]

##</code><code>##

tr/ //d;
$camel .= $_;