PARI/GP vecsort/versearch and Mod()

I wanted to check four 2x2 matrixes with entries in ℤ/2ℤ to be closed 
under matrix addition and multiplication.

Because of missing order relation for Mod() using vecsort/vecsearch 
directly was no option. So I used workaround:
https://gist.github.com/Hermann-SW/18f6fd4a991afbf6623c24e6dd089701

contains(V,M)={[m|m<-V,m==M]!=[]};

for

foreach(F4,a,
   foreach(F4,b,
     assert(contains(F4,a+b),"add not closed")));

With only 4 elements that is OK, but for more binary vecsearch would be 
nice to have.


I defined vecsort cmpf, but because nested braces are not allowed, this 
looks not nice:

...
   slF4 = vecsort(lift(F4));
}
   inF4(M)={vecsearch(slF4,lift(M))};
{
...

for

assert(inF4(a+b),"add not closed")


Trying to get rid of 2nd and 3rd brace I tried

   inF4(M)->vecsearch(slF4,lift(M));

but that does not work. Is there a cmpf definition that works inside 
braces?

Regards,

Hermann.