I guess the problem is in the $s variable, looking in the source I see <center class=categories>, notice there's no quoting in "categories".

this works for me:

use LWP::Simple;

$html = get "http://search.cpan.org/";

$s = '<center class=categories>';
$e = '</center>';

$txt = substr $html, index($html,$s), index($html,$e);
print "$txt\n";
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