Perl 竖向统计字母出现个数

统计第二列，每一竖行的字母的个数：

测试数据如下：
AB78954    QDKLJLKASJDFQIPQRUWEIRJPFMQPJEFIJWEFQPEIJFQWJEPIJFQ
AB78955    JAUTUSADTFUDIADCHEUWYFOUYSOUDIFYOUIWEYFHJKASDFHQK
AB78956    IEOUQFMFAJDSKHFUYDCHIUVOHASDUNOHUEHRQOIUHFAOIUSHF
AB78957    NVCNQJEOYUFIEWFNMDNCOEUWCQNCONVXCNBVOQYEWBYEB
AB78958    UOWEYFHBVMXCBVHOBWEUYBVYEBVMNBVHJBOEUFPEUIYPEIY
AB78959    UIQOYTUIQTPOEIWUTHVZXCBNVMANBOEYQFWYFGOUYEGFUWEIF
AB78960    QDKLJLKASJDFQIPQRUWEIRJPFMQPJEFIJWEFQPEIJFQWJEPIJFQ


我写的代码：    （可能不是最好的，有高手请指正）

#!/usr/bin/perl

use strict;
use warnings;

my @str;
my %has;

my @rows;

while (<DATA>)
{
    my ($f,$l) = split /\s+/;
    my @rows = split //,$l;
    my $col = 0;
    foreach (@rows)
    {
        $has{$col}{$_}++;
        $col++;
    }
}

my @kyes = sort keys %has;



foreach my $key (@kyes)
{
    print "$key\n";
    my @ks = sort keys %{$has{$key}};
    foreach my $k (@ks)
    {
        print "\t$k\t$has{$key}{$k}\n";
    }
}



__DATA__
AB78954    QDKLJLKASJDFQIPQRUWEIRJPFMQPJEFIJWEFQPEIJFQWJEPIJFQ
AB78955    JAUTUSADTFUDIADCHEUWYFOUYSOUDIFYOUIWEYFHJKASDFHQK
AB78956    IEOUQFMFAJDSKHFUYDCHIUVOHASDUNOHUEHRQOIUHFAOIUSHF
AB78957    NVCNQJEOYUFIEWFNMDNCOEUWCQNCONVXCNBVOQYEWBYEB
AB78958    UOWEYFHBVMXCBVHOBWEUYBVYEBVMNBVHJBOEUFPEUIYPEIY
AB78959    UIQOYTUIQTPOEIWUTHVZXCBNVMANBOEYQFWYFGOUYEGFUWEIF
AB78960    QDKLJLKASJDFQIPQRUWEIRJPFMQPJEFIJWEFQPEIJFQWJEPIJFQ