The information required is the path connecting the various codes. So if you start at basic level you can see that in the example I gave

'fr065601' connects to  'fr065600', 'fr065602'
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Now taking it to level 1

'fr065601' connects to 'fr065600', 'fr065601' , 'fr065602'
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This is found by looking up the values 'fr065600', 'fr065602' as keys in %partners and finding their values.

This could continue for many levels

('fr065601' connects to 'fr065600', 'fr065601' , 'fr065602' , 'fr06560
+4' , 'fr065602' )
[download]

The snippet I included does achieve this for 2 levels