johngg@abouriou ~/perl/Monks $ perl -Mstrict -Mwarnings -E '
my $digs    = q{0,1,2,3,4,5,6,7,8,9};
my $globStr = qq|{$digs}| x 4;
my %combs   =
   map  { $_ => 1 }
   grep { ! m{(.).*\1} }
   map  { join q{}, sort split m{} }
   glob $globStr;
say for sort keys %combs;' | wc -l
210