c:\@Work\Perl>perl
use strict;
use warnings;

my %test_hash = ("foo_bar" => "baz");
my $test = "foo";

my $var5 = qq{aaa/$test_hash{ qq{${test}_bar} }};  # qq{} in qq{}
print "var5 = '$var5' \n";
^Z
var5 = 'aaa/baz'