kanthsri has asked for the wisdom of the Perl Monks concerning the following question:

Belowis the code that executes in system but not executing in my system 
use LWP::Simple;
use URI::Escape;
use HTML::TreeBuilder;
use Try::Tiny;

my $look_for = "perl";

my $contents
  = get "http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dstr
+ipbooks&field-keywords="
  . uri_escape($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_trimme
+d_text };
 
    print "$author\n";
}
$html->delete;

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  • Comment on Use of uninitialized value in subroutine entry at C:/Perl/lib/HTML/TreeBuilder.p m line 108.
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Re: Use of uninitialized value in subroutine entry at C:/Perl/lib/HTML/TreeBuilder.pm line 108.
by Athanasius (Archbishop) on Dec 26, 2012 at 06:59 UTC

    Hello kanthsri, and welcome to the Monastery!

    I re-formatted your code as follows:

    #! perl
use Modern::Perl;
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 { $item->look_down(class => 'ptBrand')->as_trimme
+d_text };
    print "$author\n";
}

$html->delete;

    [download]

    and ran it with the following result:

    16:54 >perl 452_SoPW.pl
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

16:56 >

    [download]

    What output do you get? In what way is the code “not executing” in your system?

    Update: Just realised that the title answers my question! What version of HTML::TreeBuilder are you running? Mine is v5.01. What is line 108 in your version of this module?

    Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

[reply]
[d/l]
[select]
      v5.16.1 this is my version of perl and in treebuillder.pm the unitialised value is $new->parse($whunk);
[reply]
        this is the version of treebuilder v5.02
[reply]
Re: Use of uninitialized value in subroutine entry at C:/Perl/lib/HTML/TreeBuilder.p m line 108.
by 2teez (Vicar) on Dec 26, 2012 at 06:49 UTC

    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
[reply]
[d/l]
[select]
      Thank you for getting information about <code> tag for formatting.But the output is same.
[reply]
Re: Use of uninitialized value in subroutine entry at C:/Perl/lib/HTML/TreeBuilder.p m line 108.
by Anonymous Monk on Dec 26, 2012 at 08:12 UTC
[reply]

      i tried it .. butgetting the same result..

[reply]

        So $contents is undef, meaning get() failed to get anything

[reply]

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