use strict;
use Date::Calc qw(check_date);

## my ($month, $day, $year) = (2, 29, 2036); ## valid
my ($month, $day, $year) = (2, 29, 2037);    ## invalid, will set to defaults

## You could use dynamic date values instead
my ($def_month, $def_day, $def_year) = (2, 7, 2002);

if (not check_date ($year, $month, $day)) {
   print "Invalid date was entered ($month/$day/$year)! ",
         "Default date will be used instead.\n";
   ($month, $day, $year) = ($def_month, $def_day, $def_year);
}

print "Using date: $month/$day/$year\n";