Monks,

The first example code of HOP is something like this (I added print statements): 
sub binary {
  my ($n) = @_;
  return $n if $n == 0 || $n == 1; 
  my $k = int($n/2);
  my $b = $n % 2;
  print "n is $n.\nk is $k.\nb is $b.\n";
  print "above\n";
  my $E = binary($k);
  print "below\n";
  print "n is $n.\nE is $E.\n\n";
  return $E . $b;
}

print binary(8);

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And the output: 
n is 8.
k is 4.
b is 0.
above
n is 4.
k is 2.
b is 0.
above
n is 2.
k is 1.
b is 0.
above
below
n is 2.
E is 1.

below
n is 4.
E is 10.

below
n is 8.
E is 100.

1000

[download]
The program "loops" 3 times before the final return. Obviously it is not a simple loop, though, and that is what confuses me. I don't understand the recursion process. I naively expect above/below above/below above/below return sequence, rather than above/above/above below/below/below return.

UPDATE: And notice the sequence of "n" value is an inside-out sequence. What?

I'm not seeing this, please help me understand. Thanks.

UPDATE 2: Thanks to all Monks for your generous and informative replies. PerlMonks is certainly the best resource for information in the Perl Community.

In reply to recursion basics by wrinkles

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