use strict;
use Carp;

sub compare_TSD {
    my %tsd;
    my ( $tsd{up}, $tsd{dn} ) = @_;
    croak "compare_TSD called without two defined values"
        unless ( defined $tsd{up} and defined $tsd{dn} );

    my $return_status = '';
    for my $arg ( qw/up dn/ ) {
        my $str = $arg;
        $str .= " has unusable characters," if ( $tsd{$arg} =~ /[^ACGT]/ );
        $str .= " has wrong character count," if ( length( $tsd{$arg} != 10 );
        $return_status .= " $str" if ( $str ne $arg );
    }
    return $return_status if ( $return_status ne '' );

    return "perfect match" if ( $tsd{up} eq $tsd{dn} );
    # not sure what else needs to be checked...
}