Observe the following code:

 
#!/usr/bin/perl 

use strict; 
use HTML::LinkExtor;

my $html = <<EOF
<p>
    <a href="http://example1.com/">
        Example 1
    </a>
</p>

<p>
    <a href="http://example2.com/">
        Example 2
    </a>
</p>

<p>
    <a href="http://example3.com/">
        Example 3
    </a>
</p>

EOF
;
# Print them out

print "Here's all links:\n";
my @return  = find_my_links($html); 
print join("\n", @return), "\n";

print "Here's all links #2:\n";
my @return2 = find_my_links($html); 
print join("\n", @return2), "\n";



sub find_my_links { 

    my $str = shift; 
    my @links = (); 

    sub callback {
         my($tag, %attr) = @_;     
         return if $tag ne 'a';  # we only look closer at <a ...>
         my $link =  $attr{href}; 
        push(@links, $link);         
    }

    my $p = HTML::LinkExtor->new(\&callback);
    $p->parse($str);
    undef $p; 
    undef $str;
    return @links; 

}
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In this barebones example, I want to grab the links in found in $str, and I encapsulate all my stuff in the find_my_links() subroutine.

Easy enough, and it works! Once. If I call the parse() method twice, the second time will return an empty list. Why?