=head2 C<decode_COMP3>

Decodes a COMP3 BCD-number with trailing sign

=cut

sub decode_COMP3 {
    # Cut off the last nibble
    # 0C -> +
    # 0D -> -
    # 0F -> (unsigned number)
    my $digits = unpack "H*", $_[0];
    my $sign = chop $digits;
    #print "$digits\n";
       if ($sign eq 'D' or $sign eq 'd') { $sign = '-' }
    elsif ($sign eq 'C' or $sign eq 'c') { $sign = '+' }
    elsif ($sign eq 'F' or $sign eq 'f') { $sign = ' ' }
    else { $digits .= $sign; $sign = '?' };
    "$sign$digits"
};