$ perl -le 'my $str="0123456789"; for my $x (0 .. 9) { $str =~ s/$x/./g; print $str;}'
.123456789
..23456789
...3456789
....456789
.....56789
......6789
.......789
........89
.........9
..........
$ perl -le 'my $str="0123456789"; for my $x (0 .. 9) { $str =~ s/$x/./og; print $str;}'
.123456789
.123456789
.123456789
.123456789
.123456789
.123456789
.123456789
.123456789
.123456789
.123456789