c1 = 'A'
isLetter = /[[:alpha:]]/.match?(c1)
isNumber = /[[:digit:]]/.match?(c1)
# isLetter is true
# isNumber is false
c2 = '$'
symbolList = "@#$%^&*"
isInList = symbolList.include?(c2)
# isInList is true
puts "isLetter is #{isLetter}"
puts "isNumber is #{isNumber}"
puts "isInList is #{isInList}"