get '/search_db/:opt1/:opt2' => sub {
    die 'search_db';
    # ...
};

function check_id() {
    $.ajax({
        type: 'GET',
        url: '/search_db/check_id/3',
        success: function( data ){
            console.log( data );
        }
    });
    alert( 'hallo' );
};