#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

say my $search_for_species = 'O4';

while (<>) {
    my %counts;
    my @species = split;
    my @numbers = split ' ', <>;
    warn "Different number of columns at line $.!" if @species != @numbers;
    for my $i (0 .. $#species) {
        $counts{ $species[$i] } = $numbers[$i];
    }
    say $counts{$search_for_species} // 0;
}