#!/usr/bin/perl -w
use strict;

my @cnt = qw(A2G G2A C2T T2C A2T A2C G2T G2C);
my %cnt;

for my $change (@cnt) {
    my ($c1, $c2) = split /2/, $change;
    $c2 =~ tr/ATCG/HRDZ/;
    my $x = $c1 ^ $c2;
    $cnt{$change} = eval "sub { \$_[0] =~ tr/$x/$x/ }";
}

my $seq1 = "AAAGATCGTG";
my $seq2 = "AGTACTTTCC";

(my $tmp = $seq2) =~ tr/ATCG/HRDZ/;
my $diff = $seq1 ^ $tmp;
    
print join("; ", map { $_."=".$cnt{$_}->($diff) } @cnt ), ".";

__END__
A2G=1; G2A=1; C2T=1; T2C=1; A2T=1; A2C=1; G2T=1; G2C=1.