sub fastolfe {
        my $source = shift;
        my $chop   = shift;
        local($_);

        my %found;
        $found{$_}++ while ($_ = chop($source)) ne '';
        while (($_ = chop($chop)) ne '') {
                return if --$found{$_} < 0;
        }

        my $result;
        foreach (sort keys %found) {
                $result .= $_ while $found{$_}--;
        }
        $result;
}