nil already evaluates as 'false'

No need to compare with 'nil'
Better names for num1 and num2

I'm trying to clearly understand the sorting algorithm.
(Yes... I'm not good at them ;-) )
Better names for value1 and value2
Fix a bug with the 'reset'

Making the word 'reset' the conditional introduces a bug.
You'll never be able to sort correctly if the user enters 'reset' as one of the words.
Changed it for Symbol (the user can't enter a Symbol at the keyboard)