date_regex,pl

#
# Validate dates of type DD.MM.YYYY
# consider number of days in month and leap years
# also year span is from 1900 to 2999
#
my $re = qr{
    ^(?:(?:31\.(?:0?[13578]|1[02]))\.|(?:(?:29|30)\.(?:0?[1,3-9]|1[0-2])\.))(?:(?:19|2\d)?\d{2})$
    |
    ^(?:29\.0?2\.(?:(?:(?:19|2\d)?(?:0[48]|[2468][048]|[13579][26]))))$
    |
    ^(?:0?[1-9]|1\d|2[0-8])\.(?:(?:0?[1-9])|(?:1[0-2]))\.(?:(?:19|2\d)?\d{2})$
}x;

my @dates = qw/
01.12.2000
01.01.2000
31.01.2000
30.11.2999
31.01.1899
31.01.1900
21.01.1900
01.01.3000
20.06
5
xxx
/;

for (@dates) {
    print "date: $_";
    print /$re/gm ? ' matches!' : ' not match.';
    print "\n";
}