I hadn't used HTML::TokeParser::Simple before, but I just tried it now, and it works fine for me even after removing the second call:

my $p = HTML::TokeParser::Simple->new($ARGV[0]);
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So it seems logical that you would only instantiate the object once at the beginning.

(Update:  Whoops ... not necessarily the case, as several wiser monks have gently instructed below.)

A couple of points I'd mention, though.  First, if you add:

use strict;
use warnings;
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at the beginning of your code, you'll see that you've redefined $p.  (The strict and warnings pragmas are considered good programming practice, as they will catch a lot of things that might otherwise cause you problems -- it's a good idea to use them in all your programs).

Secondly, it might be more helpful to the user (or even yourself!) if you give an error message or a syntax message in case no argument are passed to the program.  For example:

use HTML::TokeParser::Simple;
(my $url = shift) or die "syntax:  html_test  <filename>\n";
my $p = HTML::TokeParser::Simple->new($url);
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