Geo::GeoNames provides a perl interface to the webservices found at [1]. That
is, given a given placename or postalcode, the module will look it up and return
more information (longitude, lattitude, etc) for the given placename or
postalcode. Wikipedia lookups are also supported. If more than one match is
found, a list of locations will be returned.

Before you start, get a free GeoNames account and enable it for access to the
free web service:
- Get an account [2]
- Respond to the email
- Login and enable your account for free access [3]

[1] http://api.geonames.org/
[2] http://www.geonames.org/login
[3] http://www.geonames.org/enablefreewebservice