Help with regular expression

Ryan,

I agree with Phlip. This has crossed into territory better served by a
real HTML parser. Something like this (untested):

require 'hpricot'
doc =
Hpricot("Keep<pre>Toss</pre>Keep<blockquote>Toss<p>Toss</p>Toss</blockquote>")

doc.search("//pre").each do |pre|
  pre.remove
end

doc.search("//blockquote").each do |bq|
  bq.remove
end

puts doc