my (undef, @col) = split /\t/, <>; # Column names
    my %prob_map;
    while (my ($from, @values) = split /\t/, <>) {
        @{$prob_map{$from}}{@col} = @values;
    }
    say "AAC to AAA = " . $prob_map{AAC}{AAA};
    say "AAA to AAC = " . $prob_map{AAA}{AAC};
__END__
AAC to AAA = 0.011
AAA to AAC = 0.01506

##</code><code>##

    my @col   = split /\t/, <>; # Column headings
    my @lines = map { my %l; @l{@col} = split /\t/; \%l } <>;