In addition to your chdir() and getcwd() problems, your use of glob rather than readdir has the potential of bringing you to grief.

glob("T*") will return all the files (and directories) in your current directory which contain an upper or lower case "T". There's no assurance that the directories will appear at the head of the list (it's sorted ascii-beticly). In other words, $TP_dir[0] may very well contain a file. Cconsider, for example, a directory like this:

dir
      T1
      T2
      _t.txt
      foo.txt
      bar.txt
      ~out.out
      out.c
[download]

I would expect the file "_t.txt" to appear as $TP_dir[0].

See eyepopslikeamosquito's response for the method of testing if you must use glob.

And, as others have said, please read-and-heed-and-use the Monastery's modified html markup standards and/or Markup in the Monastery so we need not go to such trouble to read your post.