The problem is that grep is always greedy. So I can make a regex like

Code:

echo "a,b,c,d,c,b,a,c" | egrep -o "([a-z]+)(,[a-z]+)*"

...and it will match the whole string, but when I start trying to use backreferences, the first ([a-z]+) will only ever match the very first variable: It will never skip past it and try other combinations when the backreference fails. There's no way to make grep non-greedy, either. Perl regexes support this though.