Expressions
===========

The language supports arbitrary complex expressions. All usual operators
are supported. The precedence of operations is as follows (with
operations being higher in the list being carried out before those lower
in the list, e.g. multiplications are done before additions.

-  expressions in parenthesis
-  not, unary minus
-  \*, /, % (modulus, as in C)
-  +, -, & (string concatenation)
-  ==, !=, <>, <, >, <=, >=, contains (strings!), startswith (strings!)
-  and
-  or

For example, "not a == b" probably returns not what you intended. The
script processor will first evaluate "not a" and then compare the
resulting boolean to the value of b. What you probably intended to do is
"not (a == b)". And if you just want to test for inequality, we highly
suggest to use "!=" or "<>". Both are exactly the same and are provided
so that you can pick whichever you like best. So inquality of a and b
should be tested as "a <> b". The "not" operator should be reserved to
cases where it actually is needed to form a complex boolean expression.
In those cases, parenthesis are highly recommended.