QEMU более 4 последовательных портов

#!/usr/bin/perl
use warnings;
use strict;

my $first_line = <>;
my $second_line = <>;

if (substr($first_line, 0, 1) eq substr($second_line, 0, 1)) {
     print $first_line;
} else {
     # You didn't say what to do if the character are different.
}