sub oddDigitSum {
    my @signed_integers_to_work_on = @_;

    my @ans;

    for (@signed_integers_to_work_on) {
        ...

##</code><code>##

sub oddDigitSum {
    my @supplied_signed_integers = @_;

    my @ans;

    for my $signed_int (@supplied_signed_integers) {
        if ($signed_int !~ /^-?\d+$/) {
            die "Parameter '$signed_int' isn't a signed integer";
            ...