Version: 0.10

Licence: Public Domain

Valid queries:
- any number (up to five digits) - will calculate the check letter
- any number followed by letter - will make sure it's valid. If not check for swapped letters
- any number followed by letter with an underscore in place of one or more numbers - show what that number could be
Valid letters are "Y", "A", "C", "D", "E", "F", "K", "M", "P", "T", "X".