bash-4.2$ ls -A
x.c x.cc x.Cc .x.(c\|C\|cc\|CC\|h\|H) x.h x.hc
x.C x.cC x.CC x.ch x.H x.hh
bash-4.2$ find . -regex '.*\.\(c\|C\|cc\|CC\|h\|H\)'
./x.C
./x.H
./x.c
./x.h
./x.CC
./x.cc
bash-4.2$ find . -name '.*\.\(c\|C\|cc\|CC\|h\|H\)'
./.x.(c|C|cc|CC|h|H)