Need info on "Component Templates". Need to extract common functions into generic tpl

System

Hi,

I am trying to get some information on "Component Templates".

My requirement is to extract common perl functions into a generic tpl file.
Say file A.tpl has common functions and I want to use these functions in B.tpl then i need to know the code to be written in B.tpl
I tried <iw_include pt ='B.tpl'>. but it didn't work.
I think using "component template", it is possible.

Can someone please provide some information about component template or any other approach to create functions in one tpl file and call them from other tpl file.

Thanks,
Rakesh.