My current fav is HTML::TagFilter, it allows you to easily strip all HTML or to allow/disallow certain tags based on innumerable attributes. It's a subclass of HTML::Parser. This is particularly useful if you want to allow certain tags, such as for text formatting.

use HTML::TagFilter;
# This will strip all HTML from whatever you pass it.
my $filter=HTML::TagFilter->new(allow=>{},strip_comments=>1);
#fieldvalue appears magically from somewhere;
$fieldvalue=$filter->filter($fieldvalue);
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-Any sufficiently advanced technology is
indistinguishable from doubletalk.