Well, the easiest way is 'literalize' the left bracket. Say that you have captured your user's post into the variable $posted_html. Simply substitute all occurances of < with &lt;

$posted_html =~ s/</&lt;/g;
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This will disable ALL rendering of HTML tags. It also has the side effect of displaying what the user tried to submit. You could also try to strip out the tags, but this is really a fine art. What if you want to allow some tags like <b> and <u> but disable others like <a> and <script>. Your code will need to be sophisticated. Incidentally, this is what the code in Why I like functional programming addresses.

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)