mod11

Modulo11 checksums are generally used to provide protection against
human errors. Typical examples include creditcard numbers, bank
account numbers or invoice numbers. If input passes then it is not said
it is correct, but simple human errors like typo's or switching numbers
can be easily cought.
The module allows to generate checksums, validate them and to iterate
them in a text (eg. search a file with bank transaction details for
valid invoice numbers)