Wouldn't it be more useful to have an intersection operator in regular
expressions? That is, the pattern 'A\&B' would match anything that is
matched by both A and B. If A and B have parenthesized subexpressions,
both sets of parentheses would match and would count.
Assuming concatenation has higher precedence than \&, the requested
behavior could be achieved via:
grep '.*X.*\&.*Y.*\&.*Z.*'
This approach would allow intersection to be nested inside other
operations. Also, it would clarify how other features work. For example,
grep -o has clear semantics with this approach, whereas the semantics of
grep -o are not so clear with the proposed --and option.
