In your original post, the line of output "aliases: ARRAY(0x55f6da24f8f0)" is clearly the only output of the statement "print "aliases: " .$_->aliases(),"\n" for (@retrieved_objs);". The fact that there is only one such line tells us that there is only one element in the array @retrieved_objs. The content of that line tells us that the element is a reference to an array. NetWallah's solution starts by dereferencing that reference. The join is his way of formatting that array for printing. Without documentation for your module, I cannot tell you why you have only one object or what that object should contain.