#!/usr/bin/perl

use strict;
use warnings;

print base_point_movement($_),"\n" for (
          1.5553 - 1.5552,
          0.9984 - 0.998,
          100.25 - 100.3,
      );

sub base_point_movement {
    my $diff = shift;
    (sprintf "%+e", $diff) =~ /([+-]\d)\./;
    return $1;
}