my %big_ash;
my @keys;
while(<DATA>) {
    my @fields = split /--+/, $_;
    next unless @fields;
    if($. == 1) { #first line
        @keys = @fields;
        next;
    }
    my %nr;
    @nr{@keys} = @fields;
    $big_ash{$nr{NR}} = \%nr;
}

print "$big_ash{14}{Dates}\n";

__DATA__
NR------E-mail----------Comment---------Dates-------------Age--Action_date
12------Tom@info.com----blablabla-------AM0,PM0,AM1,PM1---32---10-10-2001
13------Frank@info.com--blablabla-------AM0,PM0-----------45---10-10-2001
14------Sand@info.com---blablabla-------AM1,PM1,PM2-------47---10-10-2001
14------Sand@info.com---blablabla-------AM1,PM1,PM2-------47---12-10-2001

##</code><code>##

$nr{Dates} = [split ',', $nr{Dates};