If it outputted properly from the command line, there is little chance that the error is due to a LWP module installation error.

Also, why would you not just print:

use LWP::Simple;
print "Content-type: text/plain\n\n";
print "Test for LWP::Simple::get\n;
$content=get('http://adcn.com/index.html');
print "$content";
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