my $source_pos = 0;
my $end_string = $str_with_dash;
for (my $i = 0; $i < length $str_with_dash; $i++) {
    next if substr($str_with_dash, $i, 1) eq '-';
    substr($end_string, $i, 1) = substr($str_no_dash, $source_pos, 1);
    $source_pos++;
}