You can also use core module Time::Local

use Time::Local qw( timelocal );

my $date_str = '2-31-2006';

my ($m, $d, $y) = $date_str =~ /^(\d+)-(\d+)-(\d+)$/
   or die("Invalid input format. Use day-month-year.\n");

my $time = eval { timelocal(0, 0, 0, $d, $m-1, $y) }
   or die("Invalid date: $@\n");

# For Time::Local < 1.04. Perl >= 5.8.0 doesn't need this.
(localtime($time))[3] == $d
   or die("Invalid date\n");
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Update: After doing some testing, I've found that Time::Local's checking is pretty dumb (Update2:) in version < 1.04. Specifically, it assumes every month has 31 days. I added a statment — the last one — to the snippet in this node to fix the problem.

As a function:

use Time::Local qw( timelocal );

sub is_valid_date {
   my ($date_str) = @_;

   my ($m, $d, $y) = $date_str =~ /^(\d+)-(\d+)-(\d+)$/
      or return 0;

   my $time = eval { timelocal(0, 0, 0, $d, $m-1, $y) }
      or return 0;

   # For Time::Local < 1.04. Perl >= 5.8.0 doesn't need this.
   (localtime($time))[3] == $d
      or return 0;

   return 1;
}

print(is_valid_date('1-31-2006') ? 'valid' : 'invalid', "\n");
print(is_valid_date('1-32-2006') ? 'valid' : 'invalid', "\n");
print(is_valid_date('2-29-2006') ? 'valid' : 'invalid', "\n");
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