tye, well there is a reason not to simplify like you suggested:

s#<div class="blockqte">#<pre>#g;  # this is OK
s#</div>#</pre>#g;                 # this creates the problems
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you replace all </div> with </pre> and if I understood it correctly, not all the <div> tags have the attribute class="blockqte" and should be replaced ... ;-)

-- Hofmator