app_func.pm
Functions used by all other scripts: print page_header (whith navigation bar, window-title and app.-logo), print page_foot, connect to database, define colors and what not)

With regards to the printing functions, that sounds like what you actually want to do is have a look at the various templating modules, such as the shooting star Template Toolkit II.

Update: perrin wrote a very good article for Perl.com on Choosing a templating system.

Makeshifts last the longest.