Re use strict;, you said:

"since I am a mere beginner and I prefer to add it in after I have finished and tested my program."

To me, and (I strongly suspect) to many other Monks, this is evidence that you don't understand the purpose or benefits of invoking the pragma.

Rather than an (add-in||nice-to-have||safety valve), strict exists in large measure to help you get your program "right" whilst finishing and testing (and anything else). If you start coding with strict in use, perl will provide valuable information about any errors anytime you look for them.