use strict; use warnings; my %frequencies; my $maxCol = 0; while () { chomp; my ($name, $seq) = split; next unless defined $seq; my @letters = split '', $seq; ++$frequencies{$letters[$_]}[$_] for 0 .. $#letters; $maxCol = $#letters if $maxCol < $#letters; } for my $letter (qw"A T G C") { $frequencies{$letter}[$_] ||= 0 for 0 .. $maxCol; print "$letter @{$frequencies{$letter}}\n"; } __DATA__ fred ATGTTGTAT fred1 ATCTTATAT fred2 ATCTTATAT #### A 3 0 0 0 0 2 0 3 0 T 0 3 0 3 3 0 3 0 3 G 0 0 1 0 0 1 0 0 0 C 0 0 2 0 0 0 0 0 0