use strict;
use Math::BaseCalc;

### Change the three lines below to ensure your coding is unique

my $key_bitxor = 1231456789;
my $key_multip = 3;
my @key_digits = ( 'N' .. 'Z', 2 .. 9, 'a' .. 'm', 'A' .. 'M', 'n' .. 'z' );

### Coding and decoding functions

my $bcalc = Math::BaseCalc->new( digits => \@key_digits );

sub numeric_obfu {
  my $number = shift;
  my $flipped = ( $number * $key_multip )  ^ $key_bitxor;
  $flipped =~ s/^(\d+?)(0*?)$/reverse($1).$2/e;
  return $flipped;
}

sub numeric_defu {
  my $result = shift;
  $result =~ s/(\d+?)(0*?)$/reverse($1).$2/e;
  $result = ( $result ^ $key_bitxor ) / $key_multip;
  return $result;
}

### Print sample cases

my @tests = ( 0..10, 998..1004, 9999995..10000004, 99999990..99999999 );
foreach my $sample ( @tests ) {  
  my $obfu = numeric_obfu( $sample );
  my $code = $bcalc->to_base( $obfu );
  my $dcod = $bcalc->from_base( $code );
  my $defu = numeric_defu( $dcod );
  print "Converted $sample : $obfu : $code : $dcod : $defu : " . 
	( $defu == $sample ? 'OK' : $dcod) . "\n";
}