my (%f_count,%n_count); for my $file (@files) { open( my $fh, '<', $file ) or die "Couldn't read '$file': $!"; while (my $line = <$fh>) { chomp $line; next unless $line; my ($name,$number) = split(',',$line); $n_count{$name}++; $f_count{$name}{$file}++; } }