For this, I'd use instead:

use strict;
use warnings;

my $text="<tr><td>1</td><td>2</td><td>qw<font>3</font></td><td>4</td><
+tr>";
my @blocks = split /<td>(.*?)<\/td>/, $text;
foreach my $block (@blocks) {
    if($block =~ /3/) {
        print $block."\n";
    }
}
[download]

outputs

qw<font>3</font>
[download]

But you should consider one of the many HTML parser modules.