note Not_a_Number <c>use 5.010; my %parsed; while ( <DATA> ){ my @tmp = split; $parsed{$tmp[0]}{x1}++ if $tmp[1] eq '1_x'; $parsed{$tmp[0]}{c3}++ if @tmp > 2; } for my $k ( sort keys %parsed ) { say join ' ', $k, $parsed{$k}->{x1}, $parsed{$k}->{c3}; } __DATA__ A 1_x 9_z A 1_x A 1_x g_z B 2_c B 1_x 1_z C 1_x 1_z C v_x 8_z</c> <br> <p><b>Update:</b> The output part of the above code breaks for a given ID if (a) '1_x' never appears in column 2, or (b) '1_x' appears in column 2 but there is never a third column for this ID. To understand what I mean, add the following lines to <c>__DATA__</c>:</p> <c>D v_x s_x E 1_x</c> <p>Solution: change the line in the <c>for</c> loop to:</p> <c> say join ' ', $k, $parsed{$k}->{x1} || 0, $parsed{$k}->{c3} || 0; </c> 973551 973551