#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11153644
use warnings;

my $cat = { dog => '$cat->{squirrel}', squirrel => 'fred' };
my $x='$cat->{dog}/mouse';

{
my %loop;
until( $loop{ my $new = eval qq("$x") }++ ) { $x = $new }
}

print "$x\n";