1st : Tell us what you want from this script: 

I suppose it's : make someone enter a date until what he/she
types is a "good" date (in "good" format). right ? 

If yes, you loop until the entry is OK ?

2nd : the format you show is not clear  : 
      It could be : 2008, January the 1st 
                    2001, January the 8th, ... and so on
It should be better to write it MM-DD-YY (for month, day, year).  (FYI
+ :I'm french and we display dates as DD/MM/YY)

for this format, the regex "could" be:
(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])-\d\d 
but : it ignores that the maximum number of days depends on the month(
+28,29,30,31), it ignores leap years (February 28th  or 29 th ?)

You should use the function "timelocal()" from the standard module
 "Time::Local" : try to transform the date you have to validate into a
+n "epoch" time (as the function time() returns) : if the function fai
+ls, the date is wrong : 
this script seems to work:

use Time::Local timelocal;
my ($m,$d,$y);
do
{
    my $date;
    print "date (MM-DD-YY) ? ";
    $date=<>;
    chomp($date);
    ($m,$d,$y)=split(/-/,$date); 
    $m -= 1;
    $y += 1900;
}
until(timelocal(0,0,0,$d,$m,$y));
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