sub atoi {
    my $t;
    foreach my $d (split(//, shift())) {
      $t = $t * 10 + $d;
    }
  }
  $number = atoi("123");

##</code><code>##

  $string = sprintf("%f", 123.45);

##</code><code>##

   if ($string == "$string") { 
   # It is a number
   }

##</code><code>##

  if ($var =~ /(?=.)M{0,3}(C[MD]|D?C{0,3})(X[CL]|L?X{0,3})(I[XV]|V?I{0,3})/) {
    print "$var contains a number.\b";
  }