Ok.
I have a large code base of say thousands of perl files. I want to copy all calls to Mod::func() interspersed in these thousands of files to a single file, say funcCalls.pl. Then I will run fucCalls.pl and verify the output of all of the calls to Mod::func().
If the output is wrong, hopefully I will have recorded the line number and file from which each call to Mod::func() came from. In this way I will be able to fix any erroneous calls to to Mod::func().