See HTML::Element ( replace_with_content method ) and HTML::TreeBuilder

#!/usr/bin/perl -w 
use strict;
use HTML::TreeBuilder;

my $html = 
q{<tr><td>1</td><td>2</td><td><font>3</font></td><td>4</td><tr>};
my $tree = HTML::TreeBuilder->new_from_content($html);
my $td = $tree->look_down( '_tag',
                           'td',
                            sub { $_[0]->as_text =~ m/\b3/ }); 
$td->replace_with_content();
$tree->delete;
[download]

hth,
PooLpi