If you replace suggest.php with suggest.pl (or whatever your perl script is called) in the javascript, you should be able to get the value using the CGI module:

use CGI;
my $q = CGI->new;
my $word = $q->param('word');
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Update: Looking at Don Coyote's comment below I should clarify that I am assuming you are using jQuery (it certainly looks like that to me) where the $.get() sends a conventional url encoded get request, i.e. not a JSON request.