if you are simply looking for what to do if you get no parameters or unexpected parameters,
if(!$query->param){
     do_stuff();
}elsif($query->param('loc')){
     do_something_with($query->param('loc'))
}else{
     error_page(); #for invalid parameters
}

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is another way

In reply to Re: check for undefined param name by thunders
in thread check for undefined param name by cameltrader

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