add is some way to get the list of know currency abbreviations (and their full-length names), so that you could trap an unknown currency spec before sending it off to Yahoo via Finance::Quote

I updated code with Locale::Currency::code2currency() checks to avoid querying Yahoo with invalid ISO 4217 codes. However, there are some valid codes that are not available either, like ADP (Andorran Peseta).

show the clueless user what the available currency codes/names are

The problem is that most of the 203 codes in ISO 4217 are not available via Finance::Quote, so the list would not be very accurate in terms of helping a clueless user.

Update: fixed broken module links.