Here is the way I was shown, just put the module names into a hash reference:

  use strict;
  require 'foo_bar.pl';  #currently using require for these
  require 'foo_batz.pl'; #intention is to fold them into the 
                         #script after development 

  my $mods = {
      'Bar'  => 'Foo::Bar',
      'Batz' => 'Foo::Batz',
  };
  my @Stack = ();
  my $type = "Bar" || "Batz";
  do_phu($type);

  sub do_phu {
      my $class = shift;
      my $temp_obj = $mods->{$type}->new();
      push( @Stack, $temp_obj ); # point of failure
  }
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