use warnings;
use atrict;

open MYFILE, '<', $data_file
    or die "Could not open '$data_file' because $!";

my $energy;
while ( <MYFILE> ) {
    if ( /\bENERGY\b/ ) {
        ++$energy;
        next;
        }
    my ( $key, @fields ) = grep $_, split;
    for my $field ( @fields ) {
        print "$key $field $energy\n";
        }
    }