A variable definition consists of a type and a list of identifiers
that are not already in use for the current scope. The identifiers
must not be keywords and must not be the names of functions predefined
by the MxScript environment.
The scope for a variable is either:
The scope is limited by a surrounding block of curly
braces or by being declared inside a
A block of code uses the variable definition that is in the innermost
definition. This is the same scope as for C.
A variable is global if it is on the top level.