To elaborate on starbolin's comment, this code in process:

  $file_full_path = "$path/$_"; 

if (-d $_){ 
   ...
   process($_);
[download]

should use $file_full_path instead of $_:

  $file_full_path = "$path/$_"; 

if (-d $file_full_path){ 
   ...
   process($file_full_path);
[download]

And you should be able to kick off the whole traversal by calling process with your top-level directory:

  process($SOURCEDIR);
[download]

Do this will eliminate the while loop at the beginning of your program which essentially duplicates the code you have in the process subroutine.