.hgignore regex syntax to ignore a specific file (e.g. "core") anywhere

Suppose I have a working directory like this:

1. t.c
2. core
3. multicore
4. test1/core

I want to ignore all "core" files.

• If I use "/core$" (4) will get ignored but not (2).
• If I use "^core$" (2) will get ignored but not (4)
• If I use "core$" (2) and (4) will get ignored but so will (3) which is not what I want.

How do you do this?