One way to see (print) the contents (or "referent") of a reference is with the core module Data::Dumper:
    use Data::Dumper;
    ...
    print Dumper $sidstat{$instsid};
(See also Data::Dump, which I like a little better, but which isn't core.)

Update: See also the Perl Data Structures Cookbook and maybe also perllol for more info on dealing with complex data structures in Perl.