HTML Header Fields/Keys are Case Insensitive

Today while working with custom HTML headers I realised that the header key is case insensitive. So for example if you have a custom field called SOME_CUSTOM_ATTRIBUTE with value blah it is the same as Some_Custom_Attribute and even any permutation of upper and lower case letters SoMe_CuSTOm_aTTRibUte. The details of this can be found here in the RFC:

Each header field consists of a case-insensitive field name followed by a colon (":"), optional leading whitespace, the field value, and optional trailing whitespace.