How to make "barstate.isfirst" work for double loop "for"?

I am trying to make double loop work in Pine Editor code, inside a expression if. I would appreciate if someone could help.

When compiling it seems that code only recognize second loop for, making invalid the first one.

I tried a bunch of differents things but any of them worked.

Thanks in advance.

    if barstate.isfirst 
       for i = 0 to 499 by 1 
           array.push(ln, line.new(na,na,na,na)) 

       for i = 0 to length/k-1 
           array.push(upper,line.new(na,na,na,na))
           array.push(lower,line.new(na,na,na,na))