Does it incorporate the return code of the commands to get an approximate good/bad rating? I wonder what percentage of the CLI mistakes I make return zero anyway because it's a valid command that I simply misused.
One reason for this is that different programs have different rules for what should be escaped when, when you write a regex. For example, I think grep is a bit different from vim in this regard
I'd probably suck at it. No matter how frequently I use regex in :ex commands, I always screw up the escapes, substitutions, etc.