use warnings;

for(10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9) {
  printf "%.18g\n", $_;
}

__END__
Outputs:

10.0999999999999996
10.1999999999999993
10.3000000000000007
10.4000000000000004
10.5
10.5999999999999996
10.6999999999999993
10.8000000000000007
10.9000000000000004