cannot follow hanoi subroutine

convenientstore has asked for the wisdom of the Perl Monks concerning the following question:

Hello Monks,
I think I need some help understanding Hanoi tower program. I was just going over Hanoi in subroutine tutorial section and I can't exactly follow the program.
How does below step get --> 3 ??

I think I understand the algorithm but I don't think I understand the technique this program is using

----Move disk #3 from A to C.----

#!/usr/bin/perl -w
use strict;

sub hanoi {
   my ($n, $start, $end, $extra) = @_;
   if ($n == 1) {
       print "HELLLLLOOOOOOOOOOOOO Move disk #1 from $start to $end.\n
+";
   } else {
        hanoi($n-1, $start, $extra, $end);
        print "Move disk #$n from $start to $end.\n";
        hanoi($n-1, $extra, $end, $start);
   }
}

hanoi(3, 'A', 'C', 'B');



./perl.hanoi1
HELLLLLOOOOOOOOOOOOO Move disk #1 from A to C.
Move disk #2 from A to B.
HELLLLLOOOOOOOOOOOOO Move disk #1 from C to B.
Move disk #3 from A to C.
HELLLLLOOOOOOOOOOOOO Move disk #1 from B to A.
Move disk #2 from B to C.
HELLLLLOOOOOOOOOOOOO Move disk #1 from A to C.




  DB<2>
main::hanoi(perl.hanoi1:7):        if ($n == 1) {
                                                                      
+                                                               DB<2> 
+x $n
0  1
                                                                      
+                                                               DB<3> 
+s
main::hanoi(perl.hanoi1:8):            print "HELLLLLOOOOOOOOOOOOO Mov
+e disk #1 from $start to $end.\n";
                                                                      
+                                                               DB<3> 
+s
HELLLLLOOOOOOOOOOOOO Move disk #1 from A to C.
main::hanoi(perl.hanoi1:11):            print "Move disk #$n from $sta
+rt to $end.\n";
                                                                      
+                                                               DB<3> 
+s
Move disk #2 from A to B.
main::hanoi(perl.hanoi1:12):            hanoi($n-1, $extra, $end, $sta
+rt);
                                                                      
+                                                               DB<3> 
+x $n
0  2
                                                                      
+                                                               DB<4> 
+s
main::hanoi(perl.hanoi1:6):        my ($n, $start, $end, $extra) = @_;
                                                                      
+                                                               DB<4> 
+x $n
0  undef
                                                                      
+                                                               DB<5> 
+s
main::hanoi(perl.hanoi1:7):        if ($n == 1) {
                                                                      
+                                                               DB<5> 
+x $n
0  1
                                                                      
+                                                               DB<6> 
+s
main::hanoi(perl.hanoi1:8):            print "HELLLLLOOOOOOOOOOOOO Mov
+e disk #1 from $start to $end.\n";
                                                                      
+                                                               DB<6> 
+s
HELLLLLOOOOOOOOOOOOO Move disk #1 from C to B.
main::hanoi(perl.hanoi1:11):            print "Move disk #$n from $sta
+rt to $end.\n";
                                                                      
+                                                               DB<6> 
+x $n
0  3
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