Not really the way to check a date, it's already a lot of code and still far from being correct. Use appropriate module:

use 5.010;
use strict;
use warnings;

use DateTime::Format::Strptime;

my $strp = DateTime::Format::Strptime->new( pattern => '%m/%d/%Y %H:%M
+', );

while (<DATA>) {
    chomp;
    my $dt = $strp->parse_datetime($_);
    if ($dt) {
        say "Parsed: $dt";
    }
    else {
        say "Invalid date: $_";
    }
}

__DATA__
2/21/2012
fjfjf 97609876 afadfa
0/0/2012 99:00
1/0/2012 99:00
02/31/2012 01:55
02/21/2012 01:55
[download]