split looks like a better choice than a regex. I whittled away at this and came up with the untested: 
for (split(/:/, $$pattern)) {

    # make sure it starts and ends with spaces
    $_ = 'S0' . $_ unless /^S/;
    $_ .= 'S0' unless /S\d+$/;

    my @pieces = split(/[SF](\d+)/, $_);
    while (my ($spaces, $fills) = splice(@pieces, 0, 2)) {
        $out .= " " x $spaces .
            substr($camel, $camelcount, $fills);
    }
    $out .= "\n";
}

[download]
I'm fairly pleased with that, but might try to fit a pack in there. (How would you have used map?)

Aside, this: 

while (/(.)/g) {
        $camel .= $1 if $1 ne " ";
}

[download]
could be spelled: 
tr/ //d;
$camel .= $_;

[download]
I'm sure you can trim that down more, too. Don't forget to check out Acme::EyeDrops for a different take on things.

Update, very shortly after: You could, of course, just split on [SF] and probably get the same effect, though you'll have an empty element at the start. It may or may not be more clear that way.

In reply to Re: Reusing camel code by chromatic
in thread Reusing camel code by gmax

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