If all that was required was to add the line use strict;
to the top of your program, you would do it without asking our advice. Doing this, is going to create a huge number of error messages most of which refer to undeclared variables. You could declare these variables at the top of your file until all of these messages are satisfied. That would defeat the purpose of the change. It is unlikely that it would be of any help to anyone. Rethinking the scope requirements of every variable and declaring them appropriately is an error prone task that is probably more work than you are willing to take on. That only fixes "strict vars". If your code violates other restrictions, you could have much bigger problems. I recommend that all new code that you add should conform to strict, but the payback for fixing existing code is not worth the effort required.