I do not use a regex, and I am not sure if this will satisfy all your rules, but this may be something to start with:
#!/usr/bin/env perl
use warnings;
use strict;
my $num_good = 2;
my $num_bad = 1;
my $try;
my $target;
$target = 1122;
#$try = 1232; # good
$try = 2211; # bad
my @digits_targ = split //, $target;
my @digits_try = split //, $try;
my $cnt_right = 0;
my $cnt_wrong = 0;
for my $i (0 .. $#digits_targ) {
if ($digits_targ[$i] == $digits_try[$i]) {
$cnt_right++;
}
else {
$cnt_wrong++;
}
}
#print "cnt_right=$cnt_right\n";
#print "cnt_wrong=$cnt_wrong\n";
if (($cnt_right == $num_good) and ($cnt_wrong >= $num_bad)) {
print "good\n";
}
else {
print "bad\n";
}
Update: I like jettero's use of length and substr better than my use of split.