Can one modify a variable definition in a major mode depending on buffer name?

[Tom Browder <tom.browder@gmail.com>]

I think I can do that, with some experimentation, but can anyone confirm
that it's reasonably possible?

My use case is modifying our perl6-mode for the slight difference in
allowable identifiers between Perl 6 and NQP (Not Quite Perl).  By
convention, nqp files end in ".nqp" so that the buffer name should be a
good way to automatically change the single regex bound to a var name in
the mode file.  That would save having to write another major mode just for
such a small change.

Thanks.

Best regards,

-Tom