sub next_pwr {
  my ($x,$p) = (@_,2);  # default to next_pwr(X,2)
  my $log = log($x)/log($p);
  $log = int($log+1) if $log != int($log);
  return $p**$log;
}

##</code><code>##

{
  my %LOG = (2 => log(2));  # most common
  sub next_pwr {
    my ($x,$p) = (@_,2);  # default to next_pwr(X,2)

    # assertions, etc.
    die "illegal base: $p" if $p < 2;
    return 1 if $x == 1;
    $p = int $p;

    my $log =
      ($LOG{$x} ||= log($x)) / ($LOG{$p} ||= log($p));
    $log = int($log+1) if $log != int($log);

    return $p ** $log;
  }
}