Just for the sake of comparison, here is how the new Glib library makes memory collection easy. It's c, but maybe Perl6 will draw from Glib?

#include <glib.h>
#include <stdio.h>

/* compile with 
   gcc -o freetest  freetest.c  `pkg-config --cflags --libs glib-2.0` 
*/

int main() {
  int i,c;
  int *array = g_new0(int, 20000000);
 
 printf("check mem declared, not filled\n");
 c = getchar();

 for(i=0; i< 20000000; i++){
    array[i] = i;
   }

 printf("check mem, filled\n");
 c = getchar();

 g_free(array);
 
 printf("check mem, freed\n");
 c = getchar();
  

 return 0;
 }
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