The regex for Canadian postal codes is in upper case and requires a space, for usage it should accept upper and lower and the centre space is optional.

the following postal codes are correct and are accepted by almost every system I have ever used
M1L 2S9
M1L2S9
m1l 2s9
m1l2s9

speaking as a Canadian, almost no one uses the upper case format and the space is sometimes omitted.