unless (open(INPUT, "$inputfile"))
    {
    print "ERROR: Can't open file for reading : $!\n";

    }

##</code><code>##

open INPUT, $inputfile or die "Can't open $inputfile for reading: $!";

##</code><code>##

    my @data = split("\t", $_);

    # assigning varables

    my $did1 = $data[0];
    my $did2 = $data[1];
    my $score1 = $data[2];
    my $score2 = $data[3];

##</code><code>##

my ( $did1, $did2, $score1, $score2 ) = split "\t";

##</code><code>##

        my $sth1 = $dbh->prepare("select d_id, c_id from d where d_id 
= '$did1';");
        
        $sth1->execute();
        
        my $sth2 = $dbh->prepare("select d_id, c_id from d where d_id 
= '$did2';");
        
        $sth2->execute();

##</code><code>##

        my $sth1 = $dbh->prepare("select d_id, c_id from d 
           where d_id = ?");
        $sth1->execute( $did1 );
        
        my $sth2 = $dbh->prepare("select d_id, c_id from d 
           where d_id = ?");
        $sth2->execute( $did2 );