#!/usr/bin/perl -w
use strict;
use Date::Calc qw(check_date);

my $datestring = shift
 or die "$0: please pass a date string as the first argument\n";

if ( $datestring =~ m|^\s*(\d{2})\D*(\d{2})\D*(\d{4})\s*$|
# ^      : starting at the beginning
# \s*     : skip any initial spaces,
# (\d{2}) : get two digits (and save them... first save is $1),
# \D*     : skip any non-digits,
# (\d{2}) : get another two digits (and save them... second save is $2),
# \D*     : skip any non-digits,
# (\d{4}) : get another four digits (and save them... third save is $3),
# \s* skip any ending space
# $ : make sure you're at the end of the string
     and check_date($3, $1, $2)  # $3=year, $1=month, $2=day
   ) {
  print "valid date: $3/$1/$2\n";
} else {
  print "invalid date\n";
}