Perl calculate digit sum

This is a little Script to calculate the sum of the given number in Perl:

sub digit_sum {
    my $out = 0;
    while($_[0] =~ /(.)/go) {$out += $1;}
    return($out);
}

sub digit_sum {

my $out = 0;

while($_[0] =~ /(.)/go) {$out += $1;}

return($out);

}