Over in the Land of C, where there are no package or module specific namespaces, most of the project teams I have worked with use a 2-5 character prefix to designate which module "owns" each globally accessible symbol. These prefixes are abbreviations of the names of the modules they refer to.
Also, most of my teammates use an IDE like, for example, Eclipse, that provide source code navigation aids. I use Eclipse with the EPIC plug-in for Perl. EPIC provides the "Perl smarts" so that Eclipse's navigation aids work with Perl.
Anyway, with those navigation aids, like the "outline sidebar", "open declaration" and others, finding where a given function is defined is easy.