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

my $html = do{local $/; <DATA>};
my $h = HTML::TreeBuilder->new_from_content($html);

my $para    = $h->look_down(_tag => q{p});
my $font    = $para->look_down(_tag => q{font});
$font->replace_with($font->as_text);
print $para->as_HTML;

__DATA__
<p><font face="Verdana">one <a href="link.html">two</a> three</font></p>