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

my $hash = { domain => { foo => { bar => "baz" } } };

my $domain = "domain";
my $var1   = "foo";
my $var2   = "bar";

my $test = '{$var1}{$var2}';

my $value = eval '$hash->{$domain}'.$test;

print $value;   # "baz"