use of unquoted character classes for tr

[Mike]

This script uses the construct: tr [A-Z] [a-z]
However, it should instead use: tr '[A-Z]' '[a-z]'
In the second case, the character classes (square brackets and everything inside them) will be passed as arguments to tr. With the first case, the shell will first try to find a file which matches the expression all files named with a single character in the set [A-Za-z], and will then either pass these file names as arguments, or if they do not exist, will pass (the intended) literal string for the character classes.

How to test: Create a file named "a", in the current directory, then try to run the script.