Trouble with 'export word in module

问题

Let's mod.reb:

    REBOL[Type: module Name: mod]
    export: add 1 2

Let's test.reb:

    import 'mod

Running r3 test.reb, got:

    ** Script error: add has no value
    ** Where: do module catch case load-module apply for-each case import do either either either --anonymous--
    ** Near: ... add 3 2

Same trouble with other funcs instead of 'add.

No trouble with other names instead of 'export

No trouble inserting a dummy 'export before export: ... (!?)

Why this?

来源：https://stackoverflow.com/questions/40284088/trouble-with-export-word-in-module