AoC day 25, Perl

#!/usr/bin/perl

use strict;
use warnings;

use List::AllUtils qw(none first);

$| = 1;

my $SUBJECT_NUM = 7;
my $MOD = 20201227;

chomp( my @keys = <> );

print "Public Keys: ", join( ',', @keys ), "\n";

my $loop = 0;
my $val = $SUBJECT_NUM;
while (none { $val  == $_ } @keys) {
    $val = ($val * $SUBJECT_NUM) % $MOD;
    $loop++;
    print "Looping... $loop\r"  if ($loop % 100000 == 0);
}

print "Loop size: $loop (public key $val) \n";

my $other = first { $_ != $val } @keys;
print "Other public key: $other\n";

my $val2 = $other;
while ($loop--) {
    $val2 = ($val2 * $other) % $MOD;
    print "$loop\t$val2  \r"    if ($loop % 100000 == 0);
}

print "Encryption key: $val2 \n";