That is a text file. Just because the extension is tcl doesn't mean the content of the file isn't stored as text. It is also a small text file. If all you want to do is replace 'vitrix4' with 'vitrix5', I would just read() the file into a variable, use variable.replace('vitrix4', 'vitrix5'), and then write the variable back to the file.
Craig "Ichabod" O'Brien
Minimalist, buddhist, theist, and programmer
Current languages: Python, SAS, C++
Previous serious languages: Erlang, R, Java, VBA, Lisp, HyperTalk, BASIC