greg boyd wrote:
> test case (single line)
> abchelloabc
>
> grep does not find the line with grep -e '^hello'  nor with grep -e 'hello$'
> however, the line is output with
> grep -e '^hello' -e 'hello$'

Oooo, that's a good one.  Give your student extra credit!  As it happens, the 
bug was recently fixed by this patch by Norihiro Tanaka:

http://git.savannah.gnu.org/cgit/grep.git/commit/?id=256a4b494fe1c48083ba73b4f62607234e4fefd5

and the fix should appear in the next grep release.  However, since the patch 
was supposed to affect only performance, it appears that the bug fix was due to 
luck, and I'm taking the liberty of adding your student's test case by 
installing the attached further patch, to help prevent this bug from coming back 
in a future version.