On my system (Perl5.18.2):

#!/usr/bin/env perl
printf "%.49f\n", 14.4;
printf "%.49f\n", 10 + 14.4 - 10;
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...outputs...

14.4000000000000003552713678800500929355621337890625
14.3999999999999985789145284797996282577514648437500
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And (GNU C++).....

#include <iostream>
#include <iomanip>

using namespace std;

int main () {
  cout << setprecision(51) << endl;
  cout << 14.4 << endl;
  cout << 10 + 14.4 - 10 << endl;
  return 0;
}
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...outputs...

14.4000000000000003552713678800500929355621337890625
14.39999999999999857891452847979962825775146484375
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And (GNU C)

#include <stdio.h>

int main (void) {
  printf("%.49f\n", 14.4);
  printf("%.49f\n", 10.0 + 14.4 - 10.0);
  return 0;
}
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...produces this output:

14.4000000000000003552713678800500929355621337890625
14.3999999999999985789145284797996282577514648437500
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This is because the decimal value 14.4 cannot be perfectly represented as a fraction in the form of n/(2^m), and therefore has a non-terminating binary expansion.

The code I've shown above is first Perl, and second C++, and the third, C, just to illustrate that this is not a problem specific to just Perl. Here's yet another link that attempts to explain it: Re: shocking imprecision

Update: Here's a Lisp (Racket, a Scheme derivative) example as well:

#!/usr/bin/env racket
#lang racket

(displayln (~a 14.4 #:width 15 #:pad-string "0"))
(displayln (~a (- (+ 10 14.4) 10) #:width 15 #:pad-string "0"))
(= 14.4 (- (+ 10 14.4) 10))
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...outputs...

14.400000000000
14.399999999999
#f
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(The "#f" means "false"; 14.40 doesn't equal 14.399...)

JavaScript (minimal example):

alert(10+14.4-10);
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The pop-up displays: "14.399999999999999"

Python:

>>> print "%.49f"%14.4
14.4000000000000003552713678800500929355621337890625
>>> print "%.49f"%(10+14.4-10)
14.3999999999999985789145284797996282577514648437500
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Ruby:

$ ruby -e 'printf "%.49f\n%.49f\n",14.4, 10+14.4-10'
14.4000000000000003552713678800500929355621337890625
14.3999999999999985789145284797996282577514648437500
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SQL (sqlite):

sqlite> select 14.4 - (10 + 14.4 - 10);
1.77635683940025e-15
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package main

import "fmt"

func main() {
    fmt.Printf("%.49f\n",14.4)
    fmt.Printf("%.49f\n", 10+14.4-10)
}
---------
14.4000000000000003552713678800500929355621337890625
14.4000000000000003552713678800500929355621337890625

Program exited.
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