Badge number checker

Version: 0.12

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 sequence with one or more underscores in place of something - show what that number could be
Valid letters are "Y", "A", "C", "D", "E", "F", "H", "M", "P", "T", "X". Search for ____ (four underscores) to list all four-digit numbers.