Number 1818
1818 = 1+8+1+8 = 36   step 1 (2 digits output)
36   = 3 + 6 = 9      step 2 (single digit output)
result: 9 (final count of the digits ) 

##</code><code>##

use strict;
use warnings;

my $total1;

for my $num (1818..1818){   
     
     my $total1 = &spl($num);             
     
     print "$num == 9\n" if ($total1 == 9);
     
}

################# not working as i expected ####### case 1

sub spl{
	
my ($num1) = @_;	

my $total = 0;

$total = $total + $_ for (split '', $num1);

print "total: $total\n";

my $len = length ($total);

print "length: $len\n";

&spl($total) if ($len != 1);

print "final: $total\n";

return $total;

}


########## working perfectly #########   case 2

#sub spl{
#	
#my ($num1) =@_;	
#
#my $total = 0;
#
#$total = $total + $_ for (split '', $num1);
#
#my $len = length ($total);
#
#return $total if ($len == 1);
#
#&spl($total) if ($len != 1);
#
#}


output:
-------
total: 18
length: 2
total: 9
length: 1
final: 9
final: 18

Expected output:
----------------
total: 18
length: 2
total: 9
length: 1
final: 9
1818 == 9