its done thank you so much for your help. I was making a mistake in array index :)

Sir I have omitted the column containing alphabets but if a new 6th column is added into file, is it possible to modify the grep function? For example if the input file is

536 ENERGY = -176.2 gag
1 G 0 2 0 1
2 G 1 3 533 2
3 G 2 4 532 3
536 ENERGY = -175.9 gag
1 G 0 2 0 1
2 G 1 3 533 2
3 G 2 4 532 3


The working code is

 open(MYFILE, $data_file) || die("Could not open file!");
 {
my $energy;
while ( <MYFILE> ) {
    if ( /\bENERGY\b/ ) {
        ++$energy;
        next;
       }
       
    my ( $key, @fields ) = grep $_, split;
    for my $field ( @fields ) {
    if ( $field ne 'G' && $field ne 'A' && $field ne 'C' && $field ne 
+'G' )
    {
        print WRITE "$key $field $energy\n";
        }
    }
    }
    }
close(MYFILE);
[download]

How can I get the same output with 6th column (same as 1st column) added. As I cannot use if condition on it like i used for alphabets. Can you please guide/help me?