To see what you are getting back from your script add an alert() to your javascript:

$.get("suggest.pl", {word: $(this).val()}, function(data){
    alert(data);
    $("#myWord").empty();
    $("#myWord").html(data);
});
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You say earlier that you already have the script that deals with the db, so instead of the echo in PHP you just need print in Perl, something like:

print $q->header;

while (my $row = $sth->fetchrow_hashref) {
    my $word = $row->{'crps_word'};
    my $prob = $row->{'crps_probability'};
    my $str = $prob."----".$word;
    print qq|<option value="$word">$str</option>|;
}
[download]