Answer 1

The answer is: Whatever best fits the job!

My rule of thumb;

Bash - for a short script that might need a for loop to do something repetitively.

Perl - anything to do with some kind of text processing or file processing, especially if it's a one off. Just do a dirty nasty perl script and be done with it

Python - If it's something you might want to do again or something very like it. Then at least you have a chance of being able to reuse the script.