#!/usr/bin/env bash

#  matches any character that is not in the set of letters, digits, and question marks.
cleaned="${1//[^a-zA-Z0-9\?]}"

# all capitals and ending with ?
if [[ "$cleaned" =~ ^[A-Z]+\?$ ]] ; then
    echo "Calm down, I know what I'm doing!"
# ending with ?
elif [[ "$cleaned" =~ ^.*[a-z0-9]*.*\?$ ]] ; then
    echo 'Sure.'
# all capitals and not only digits
elif [[ "$cleaned" =~ ^[A-Z0-9]+$ ]] && ! [[ "$cleaned" =~ ^[0-9]+$ ]] ; then
    echo 'Whoa, chill out!'
# if empty
elif [[ -z "$cleaned" ]] ; then
    echo 'Fine. Be that way!'
else
    echo 'Whatever.'
fi