Geo::postcode will accept full or partial uk postcodes, validate them against the official spec, separate them into their significant parts, translate them into map references or co-ordinates and calculate distances between them.

the last two features require a postcode database to be supplied separately.

it does not check whether the supplied postcode exists: only whether it is well-formed according to british standard 7666, which you can find here:

http://www.govtalk.gov.uk/gdsc/html/frames/postcode.htm

geo::postcode will also work with partial codes, ie areas, districts and sectors. they won't validate, but you can test them for legitimacy with a call to valid_fragment, and you can still turn them into grid references.

to work with us zipcodes, you need geo::postalcode instead.