use List::Util qw/max reduce/;
 
while(<DATA>){
  chomp;
  
  #-- Version 1
  my $diff="";
  while (/(\d)(\d)/g) {
    $diff.=($2-$1)%10;
    pos($_)--;
  }	  
  my $v1= 1 + max map { length } $diff =~ m/(1+|9+)/g;
 
  #--- Version 2
  $diff="";
  reduce { $diff.=($a-$b)%10; $b} split //;
  my $v2= 1 + max map { length } $diff =~ m/(1+|9+)/g;
 
  print "V1: $v1  V2: $v2  $_\n";
}

__DATA__
461771621368210983721913243963580233112903255149955120374576