Function call identification

Dear all,

I was wondering if their exist any function in Plpgsql functions that
would allow me to identify which functions has called what function.

To make it simple suppose I have a function
func_1 ,func_2 and func_3

Now func_1 calls function func_2 for some reason and it gives the
results as required now the func_3 also nearly requires same kinda
results but with some changes .

So is their any function that can help me determine which function called func_2

Something like

IF func_call = func_2 THEN
do some blah;
ELSIF func_cal = func_3 THEN
do some more blah;
END IF:

any pointers or round approach would be helpfull.

--
With Best Regards,
Vishal Kashyap.
Lead Software Developer,
http://saihertz.com,
http://vishalkashyap.tk