use v5.12;
use warnings;

#say "Mode: ", my $mode = $ARGV[0] // 0;

use Config; say $Config{ivsize}; say $Config{nvsize};

sub test {
  my ($mode) = @_;
  say "**** Mode: $mode";
  my $now=1;
  for my $x ( 1.. 65) {
    $now =
      $mode == 0 ? 2 * $now    :
      $mode == 1 ? 2 ** $x     :
      $mode == 2 ? 2 ** $x  -1 :
      die "Mode=$mode not implemented yet";

    if ( $now == $now-1 or $now == $now+1 ) {
      print "Problem at $now = 2**$x\n";
      printf "%22u %22u %22u\n",$now-1,$now,$now+1;
      last;
    }
  }
}

test($_) for 0..2;