RegEx Case Sensitivity

[ItsDrew]

Version 4.1.10
Options > User Registration Options > Username Regular Expression

^[A-Z][A-Za-z]+\.[A-Z][A-Za-z-]+$

I'm trying to force Firstname.Lastname or Firstname-Lastname-Lastname with the first letter being forced to a capital letter. But it seems as if the code autimacially puts the lower case i at the end of the preg_match string to ignore case.

How can I remove the "i" from the preg_match code so I can force case sensitivity?