REBOL 3 Errors: dup-vars

A function was evaluated that had multiple occurrences of a word defined in its specification block. For instance, if the word arg was defined as both argument one and two.

Message:

["Duplicate function value:" :arg1]

Example:

filter-error try [f: func [a /local a][print a]]
** Script Error: Duplicate function value: a
** Where: func [a /local a] [print a]