Any pointers where I went wrong ?

Assuming '%' is needed to dereference a hash reference. Instead, you just need to put the hash reference (e.g. $href) where you would normally put the name of the hash (where "name" means not including the $,@,% sigils). So where you'd say $hash{key}, you say $$href{key} (though $href->{key} also does the trick). See references quick reference for a quick runthrough of the possibilities.