sub incdec {

  $number = shift;

  # do something if not /^\d*\.\d+$/

  return $number+1 if $number =~ /^\d+$/;

  $number =~ /\.(\d+)$/;

  return $number + ("1E-".length($1);
}

for $n (1, .004, 1.99, 1.79, 1.009999) {

  print "$n++ = ".incdec($n)."\n";
}