tie()'d objects have overhead

True, but the OP said that performance was not a concern.

... would be replacing a small basic hash with less than 4 entries with a tied hash, and an attached blessed string reference. No gain would be realized ...

My thought was to replace the 120_000 element hash with a Tie::SubstrHash which does make a considerable saving in space. However, as you can't use a Tie::SubstrHash to store references, that throws the idea in the bin.

I have an incomplete and broken version of the standard module that attempts to work around this particular restriction, but in the absence of the abilty to build XS/Inline-C, I am unable to complete that. There's no guarentee I could bring the idea to fruition anyway.