Perl in a Nutshell, 2nd Edition

The URI Module

The URI module contains functions and modules to specify and convert URIs. (URLs are a type of URI.) In addition to the URL module itself, there are also: URI::URL, URI::Escape, and URI::Heuristic. Of primary importance to many LWP applications is the URI::URL class, which creates the objects used by LWP::UserAgent to determine protocols, server locations, and resource names.

The URI::Escape module replaces unsafe characters in URL strings with their appropriate escape sequences. URI::Heuristic provides convenience methods for creating proper URLs out of short strings and incomplete addresses.