macro statement_control:<my_while>($expr, &whileblock) {
  while $expr &whileblock();
# do we need while $expr do &whileblock();    ?
}

my $i = 0;
my_while {$i < 10} {
  say "i: $i";
  my $j = 0;
  my_while {$j < 10} {
    say "j: $j";
    $j++;
  }
  $i++;
}