Please put your code in <code> tages. See How do I post a question effectively?

Update:
Run this you should have your result: Modified OP script 

use warnings;
use strict;

use LWP::Simple;
use URI::Escape;
use HTML::TreeBuilder;
use Try::Tiny;

my $look_for = "perl";
my $contents =
  get
"http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dstripbooks&
+field-keywords="
  . uri_escape($look_for);
my $html = HTML::TreeBuilder->new_from_content($contents);
for my $item ( $html->look_down( id => qr/result_\d+/ ) ) {

    #$item->dump;
    #find out structure of HTML
    my $author =
      try { $item->look_down( class => 'ptBrand' )->as_trimmed_text };
    print "$author\n";
}
$html->delete;

[download]

Output: 
by Randal L. Schwartz, brian d foy and Tom Phoenix
by Tom Christiansen, brian d foy, Larry Wall and Jon Orwant Ph.D.
by Tom Christiansen and Nathan Torkington
by Randal L. Schwartz, brian d foy and Tom Phoenix
by Johan Vromans
by Joseph N. Hall, Joshua A. McAdams and brian d foy
by Randal Schwartz, Tom Phoenix and brian d foy
by David N. Blank-Edelman
by brian d foy
by Curtis Poe
by Damian Conway
by Paul E. Hoffman

[download]
Update II:
After updating I saw Athanasius, has it too. ++ to fast fingers!!!

If you tell me, I'll forget.
If you show me, I'll remember.
if you involve me, I'll understand.
--- Author unknown to me

In reply to Re: Use of uninitialized value in subroutine entry at C:/Perl/lib/HTML/TreeBuilder.p m line 108. by 2teez
in thread Use of uninitialized value in subroutine entry at C:/Perl/lib/HTML/TreeBuilder.p m line 108. by kanthsri

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