$hash{name} = {date => "00-22-00", city=>"Chicago",};


function (\%hash1);
function (\%hash2);

##</code><code>##

sub function {
my %hashref=%{shift()};
#the below works ok
print $hashref{name}{city},"\n";
# but adding to the hash doesn't work if I print out
# the entire hash outside this function
$hashref{name}={data1=>"moredata",};
# it does work if I print it out inside the function
}