open my $annotation_read_handle, '<', $annotation_file; my %annotations_for; while (my $ad = <$annotation_read_handle> ) { # read $an_chrom out of $ad my ($an_chrom, undef) = split(/\t/, $ad); # store for future lookups push @$annotations_for{$an_chrom}, $ad; } close $annotation_read_handle;