I couldn't get your code and Time::Local to invalidate Feb. 31, 2003 08:40 by passing a ref to ('023103','08:40') so I whipped this up. As you can see, I choose to use die statements as opposed to the print and exit combo.

use Date::Calc qw(check_date check_time);

our $DEBUG = 1; # set to 0 to disable

print "woohoo!\n" if valid( ['033103','12:59'] ); # March 31, 2003 12:
+59 valid
print "w00t!\n" if valid( ['022803','13:00'] );      # February 28, 20
+03 13:00 valid
print "Yippee!\n" if valid( ['023103','08:40'] ); # February 31, 2003 
+8:40 invalid

sub valid {
    my $ref = shift;
    my $date = shift @$ref;
    my $time = shift @$ref;
    die "Invalid date format $date" unless $date =~ /(\d\d)(\d\d)(\d\d
+)/;
    my ($month, $day, $year) = ($1, $2, $3);
    $year += ($year <= 69) ? 2000 : 1900;
    die "Invalid date $date" unless (check_date($year,$month,$day));
    die "Invalid time format $time" unless $time =~ /(\d\d):(\d\d)/;
    my ($hour, $minute) = ($1, $2);
    die "Invalid time $time" unless (check_time($hour,$min,$sec));
    print "$date $time is valid.\n" if $DEBUG;
    return 1;
}
[download]

update: fixed $year update code