Examples website?

Does anyone out there know of a website which has example on how to configure 
procmail?  I am actually looking for an example which will show me how to pull 
a variable from an email and pass it off to a perl script or add the variable 
to a text file.  The example variable would be in the body of the email and 
would be something like:

bla bla bla:  123456

It would look for that line in the email and take the "123456" and pass that 
off to a script or a text file.

HELP!!

Scott