... or a naive one-liner state-machine ... 

perl -pe 'chomp; $s=!$s,next if s/^\s*<\/?pre>\s*$//i; $_="<p>$_</p>" 
+if $s; $_.="\n";' <in >out

[download]
... makes ... 
in:              out:
----------------------------------
<html>           <html>
...etc...        ...etc...
<pre>            <p>Line 1</p>
Line 1           <p>Line 2</p>
Line 2           <p>...etc...</p>
...etc...        <p>Line n</p>
Line n           ...etc...
</pre>           </html>
...etc...
</html>

[download]

In reply to Re: Substitution inside tags, as 1 line by Perlbotics
in thread Substitution inside tags, as 1 line by tel2

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
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