Your question is a little bit vague, but I do have a suggestion. You don't need to parse the query yourself, try to use HTTP::Daemon, and do something like:

my $d = HTTP::Daemon->new(LocalAddr => "localhost",
                          LocalPort => 80,
                          Listen => 20) || die;
my $c = $d->accept
my $r = $c->get_request;
if ($r) {
    my %query = $r->uri->query_form();
    #....
}
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The query would be parsed and stored in %query. Also the "+" sign has been taken care of.

BTW, the query string is not always delimited by "&", a different style uses ";", if you do it by yourself, you have to take this into consideration.