IFTE function cmd and store cmd

[compsystems]

Hello,
I want to extract the "TRUE" values from an array
[ false, false, true, true ] => [ true, true ]

In the following code there is a problem when trying to store a variable within IFTE function cmd
if I delete y: = or ▶y it works but the value of y is not updated

PHP Code:

#cas
test_IFTE( ):=
begin
  local x, y, z;
  x := 1; 
  y := []; 
  z := [ false, false, true, true ];
  index := 1;
  REPEAT 
    ifte( z[x] == true,  concat( y, true )▶y, nop ); 
    x++; 
  until 
    x == 5;
  
  return y;
 end;
#end 


[Check] No errors in the program

test_IFTE() [Enter] returns

Quote:1,[0,0,true,true,true] ???
[ true, true ] // ok

PHP Code:

ifte( z[x] == true,  y := concat( y, true ), nop ); 


// also fails

test_IFTE() [Enter] returns

Quote:"for([0,1,0,{
ifte(((z[x])==true),y:=concat(y,true),'nop');
x++;
IF x = 5 THEN BREAK ; END ;
}]) in [test_IFTE] instruction #7 error, try debug([test_IFTE])
Error: Bad Argument Value"

REQUEST: An alternative or simpler code with functions cmd and not block of structures?