!/usr/bin/perl -w -p 
s/^(\*+)/ 
$n = length($1), 
$n < $o ? @l[$n+1..$#l] = (0)x($#l-$n) : 0, 
$l[$n]++, 
$o = $n, 
join(".",@l[1..$n]) 
/e; 

##</code><code>##

!/usr/bin/perl -w -p 
s {
  ^(\*+) # look for stars at the beginning of line
}{
  my $n = length($1); # get number of stars
  @l[$n+1..$#l] = (0)x($#l-$n) if $n < $o; # @l is global
  $l[$n]++;
  $o = $n; # $o is global
  join(".",@l[1..$n]); # returning this
}ex;