my $N = setupSub( %myParameters );
while (defined( my $at = stepSub())) {
  printf "%d percent done\n", $at/$N;
}
my $results = resultsSub();


##</code><code>##

my $granularity = 5;

sub showProgress {  # will be called $granularity+1 times
  my $at = shift;
  if ($at == 0) {
    print "starting\n";
  } elsif ($at == $granularity) {
    print "done\n";
  } else {
    print "$at/$granularity done\n";
  }
}

my $results = mySub(%myParam,
  progress => {
    callback => \&showProgress,
    granularity => $granularity
  }
);