#! /usr/bin/perl

use strict;
use warnings;

my %hash = (1 => 31,
            2 => 28,
            3 => 31,
            4 => 30,
            5 => 31,
            6 => 30,
            7 => 31,
            8 => 31,
            9 => 30,
            10 => 31,
            11 => 30,
            12 => 31,);

for my $datum(qw/12.12.2004 31.02.2006 3.5.1999/){
  if($datum =~ /^(([012]?[0-9])|(3[01]))\.((0?[0-9])|(1[0-2]))\.(\d{2}|\d{4})$/){
    my ($d,$m,$y) = split /\./, $datum;
    $hash{2} = 29 if(is_leap_year($y));
    $m =~ s/^0//;
    print "yes\n" if($d > 0 && $d < $hash{$m});
  }
}

sub is_leap_year{
  my ($year) = @_;
  return 0 unless($year % 4 == 0);
  return 1 if($year % 400 == 0);
  return 0 if($year % 100 == 0);
  return 1;
}

use strict;
use warnings;

use Time::Local;

my @A  =  (
    [25, 6, 1996 ],
    [31, 2, 2005 ],
    [29, 2, 2000 ],
);

foreach my $dmy (@A) {
    my ($d, $m, $y) = @{$dmy};
    print "invalid date: $d.$m.$y\n" unless eval { timelocal (0,0,0,$d,$m-1,$y) };
}

use strict;
use warnings;

use Time::Local;

my @A  =  (
   [25, 6, 1996 ],
   [31, 2, 2005 ],
   [29, 2, 2000 ],
);

foreach my $dmy (@A) {
   my ($d, $m, $y) = @{$dmy};
   print "invalid date: $d.$m.$y\n" unless eval { timelocal (0,0,0,$d,$m-1,$y-1900) };
}

use Date::Calc qw(check_date);

@tests = (
      [25, 6, 1996 ],
      [31, 2, 2005 ],
      [29, 2, 2000 ],
     );

for (@tests) {
    my @ymd = reverse @$_;
    print "check_date @ymd ergibt " . check_date(@ymd) . "\n";
}