e there was a timeout during  the operation.
</p>

<p class=note>
<b>Important note</b>: This function was changed <em>severely</em>. It used
to support multiple patterns (but I have never seen this feature used) and
now it doesn't anymore.  Partial results used to be returned in the same
way as successful results. This last feature violated the idea that all
functions should return <tt><b>nil</b></tt> on error.  Thus it was changed
too.
</p>

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