Awesome. I benchmarked both the JSON and your clone() sub on one of my actual datasets -- with store() -- and both obviously worked really fast:

CLONE() TIME:  0 wallclock secs ( 0.18 usr +  0.00 sys =  0.18 CPU)
JSON TIME:     0 wallclock secs ( 0.16 usr +  0.00 sys =  0.16 CPU)
[download]

There are only very slight size differences in the binary files produced by store():

624924 Aug 11 12:39 sharedhash.json
622808 Aug 11 12:39 sharedhash.clone
[download]

but they still contain the same data when "retrieved". Thanks, BrowserUK.