Win32API::File has a massive warning at the top of it.

Could you be less vague? I didn't notice a warning at the top of Win32API::File...

Are you referring to:

Object Oriented/Tied Handle Interface

WARNING: this is new code, use at your own risk.

? That warning applies to the "Object Oriented/Tied Handle Interface", so don't use that interface if you don't want to. Have you looked up the word massive recently?