The FIRST Command
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Syntax:
     FIRST [VAR <name>] [STEM <name>]

Argument template:
     VAR/K, STEM/K

Function:
     The first address of the address list becomes the current one and
     is returned in the ADDRESS variable.

Argument description:
        * VAR <name>

        * STEM <name>

Results:
        * .ADDRESS.COUNT

        * .ADDRESS.x

     The following error codes can be returned in RC2:

        * RXERR_NOFIRST

        * RXERR_ENVCHANGED