Perl complains about not finding WWW/Search/PubMed.pm in its @INC, so moving the module where you put it should be enough to let it work.
There are few debug options in WWW::Search, nonetheless: first of all, try 
use WWW::Search;
print sort &WWW::Search::installed_engines();

[download]
(more or less pasted from perldoc WWW::Search) to see if PubMed is recognized correctly. Assuming it is, you could try 
use WWW::Search;
my $oSearch=WWW::Search->new('PubMed');
$oSearch->native_query(
 "lung cancer treatment",
 { search_debug=>1, search_parser_debug=>1 }
);
#... whatever ...

[download]
so that the engine will spit out some (hopefully useful) debug information.
HTH!

In reply to Re: problem with module installation by ant9000
in thread problem with module installation by dannoura

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.