This code seems to work for me if I change from nfreeze to freeze as in the code below. I'm not sure what your error means, I was unable to duplicate it. Here are two scripts that I put together to test these routines.
HTH

#!/usr/bin/perl -w
use CGI;
use Storable qw(freeze);
my $q = CGI->new();

sub make_cookie {
    $q->cookie( -name=>'Test',
                -value=>unpack("H*",freeze(['1245','foo','foopass'])),
                -path=>'/' );
}

print $q->header(-cookie=>make_cookie());
print $q->start_html(-title=>'Test cookie');

print "Cookie Set<br>";

print $q->end_html;
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and this to retrieve the cookie.

#!/usr/bin/perl -w
use CGI;
use Storable qw(thaw);

my $q = CGI->new();

sub see_cookie {
        @{ thaw( pack("H*",$_[0]) ) };
}

print $q->header();
print $q->start_html(-title=>'Test cookie');

print "Cookie Value: ", (join " -- ", see_cookie($q->cookie('Test')) )
+, "<br>";

print $q->end_html;
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Update:
I tried these scripts under mod_perl also and they work in that enviorment also (Apache::Registry), I would take a look at your Storable module.