p:error handling

Hello XProc friends,

XML Calabash gives me this back ... '[MY-PIPELINE]' comes from a @message
and then it hits a p:error step I have placed there (names changed to
protect the innocent):

[MY-PIPELINE] LOADING - myfile.xml ...
Fatal boo:HOO at file:/some/path/to/pipeline.xpl:64:53: (no message for
error)
   in [ ... ].xpl
AAABBBCCC

This is what's in my pipeline:

<p:otherwise>
  <p:error code="boo:HOO">
    <p:with-input>
      <p:inline>
        <message>AAABBBCCC</message>
      </p:inline>
    </p:with-input>
  </p:error>
</p:otherwise>

So it's working, right?

But why is XML Calabash saying 'no message for error' and how do I repair
that (for a nice clean error)?

On XProcRef, Erik suggests this usage:

<p:error code="my:error">
  <p:with-input>
    <p:inline content-type="text/plain">Put your { $msg } here</p:inline>
  </p:with-input>
</p:error>

Is there a right way to do this? What do I need to know, and what are the
tradeoffs?

Thanks for any insights or tips,
Wendell

--
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