Building tree diagram [on hold]

Suppose I have a program P11 in a directory; it calls 2 other programs P21 & P22. Each of P21 & P22 call 2-2 other programs.

i.e.

Level-1:           |--------------P11-------------|
Level-2:  |--------P21----------|    |----------P22----------|...
Level-3:  P31                 P32    P33                   P34...
       .                   .      .                     .
       .                   .      .                     . 

Just like a tree diagram having 100s of levels, 100s of nodes at each level and 1000s of nodes in total.

I need a shell script which will give me such a tree structure.

e.g. The shell script program is – ‘MYPGM.sh’.

It takes a parameter at runtime. We can provide a program name here e.g. P11. And the script gives such a tree diagram.

Not necessary that the output structure should be in such a diagram like format as given above. We can use indexing or anything you suggest. e.g. The output file could be as –

1. P11
1.1 P21 - 1.2 P22
1.1.1 P31 - 1.1.2 P32 – 1.2.1 P33 – 1.2.2 P34

i.e. Every program's index = it's parent's index + "." + its serial number in that parent program.

Just the thing is – the number of levels & number of nodes in each level is unknown, but very large.

The program syntax used to call another program is as below.:

CALL "CHILD_PGM_NAME"

Command to find the children programs in a given program is as below.:

 egrep '^CALL| CALL ' $pgm_name > call_output | cut -d'"' -f2 call_output > call_output_cut | cat call_output_cut

I am stuck at - how to loop this command to get the above stated output file.

Can anybody suggest something?