my ($f0,  $f1,  $f2,  $f3,  $f4,  $f5,  $f6,  $f7,  $f8,  $f9);
my ($f10, $f11, $f12, $f13, $f14, $f15, $f16, $f17, $f18, $f19);
my ($f20);
...
for ($idx = 0; $idx < $NUMBER_OF_ITEMS; $idx++) {

  $name = "mn" . $idx;
  $refval = eval "\$f". $idx;
  ...
}