REBOL 3 Errors: no-refine

An attempt was made to use a function refinement that didn't exist for that function.

Message:

[:arg1 "has no refinement called" :arg2]

Example:

f: func [/a] [if a [print "a"]]
filter-error try [f/b]
** Script Error: f has no refinement called b
** Where: f/b