At the risk of being insular, I might suggest breaking up the input based on the paragraph tags. This test script seems to do the trick:

$/ = "<p class=para>";

foreach (<DATA>)
{
   s/\n//g;
   print "$1\n" if /<b>(.*)<.b>/;
}


__DATA__

<p class=para><a name="watch dog"></a><b>watch dog
-</b> A big dog that makes sure that you don't do anything that you're
+ not supposed to).</p>

<p class=para><a name="WR"></a><b>wooden round -</b> A big piece of ro
+und wood.</p>
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