Controlling the 'pattern' of a value entered in a given field

Good day to all...

We have experienced issues with a field value because it does not match the recommended 'pattern'. The user needs to enter her/his id on a form and it needs to match a built-in logic. My question has to do with the control at the field level to ensure that the value entered match at list one of 3 'patterns'

- Pattern 1 = must be 6 characters --> the first five characters must be numbers and the last one must be a number (example 12345A)

- Pattern 2 = must be 6 characters --> the first 2 characters must be 0 and N (for instance 0N1234)

- Pattern 3 = must be 6 characters --> First character is the letter C, characters 2 to 5 are numbers and last character is a letter (for instance C1234A)

My questions to all the gurus are: How could I put all these requirement into one (can you share the script with me)? and more generally, where to look for instructions on how to set up a character string to match a pattern?

Thanks a bunch for your (more than welcomed) help