{
  package IAmNotInYourIsa;
  use Moose::Role;
  requires 'dothis';
}

{
  package My::CGI;
  use Moose; with 'IAmNotInYourIsa';
  use CGI;
  sub dothis { ... my $q = CGI->new ... $q->param ... }
}

My::CGI->isa('IAmNotInYourIsa');    # false
My::CGI->does('IAmNotInYourIsa');   # true!