Hi Dallaylaen,

I think that which variant is best will depend on the actual uses later on, which you won't know until you've implemented a few things using the framework. So I might design the API in such a way that it already now allows for all variants. Just a rough idea:

$request->param_arrayref( bar => '\d+',
  nonmatching => 'filter' );  # or 'croak', 'undef', etc.
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That of course raises the question of a useful default. If you can't decide on one now, then you might even go so far as to have the first version of the framework force the user to include the nonmatching option on every call. Then, once you've implemented a few web apps with the framework, you can choose a useful default. Or, perhaps even better, you could allow the user to explicitly set the default on a per-webapp level, so each user is free to decide on their preferred default behavior.

Hope this helps,
-- Hauke D