@and()

This is a simple boolean function. It takes N numeric strings; if
they're all "1" then this returns "1". Otherwise, it returns "0".
The @and function also exhibits "short-circuiting": if any argument
is not "1", arguments after that will not be evaluated.

Usage:
@and("1", "1")
@and(@eq("a", "b"), @eq("a", "a"))
@and("0", @tell("%#", "Not displayed."))