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";
}
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Update: I like jettero's use of length and substr better than my use of split.