This question got answered in #moose on IRC, but just so that Perlmonks has the answer, here you go.

The conflict is in the Moose export &with and the Error export &with. There are a couple of solutions possible:

• Since Moose uses Sub::Exporter it is possible to rename &with in the export, like so:

  package Foo::Role; 
  use Moose::Role; 
  
  package Foo; 
  use Moose with => { -as => "moose_with" }; 
  use Error qw(:try)
  moose_with("Foo::Role"); 
  
  Foo->does("Foo::Role") # returns true
  [download]

• Or, use a different Exception module, Exception::Class is an excellent choice and known to work work just fine with Moose.