SPUG: sorting hierarchical section numbers

[Michael R. Wolf]

I want to sort strings that represent outline numbers.  

1
1.1
1.2
1.3
1.3.1
1.3.2
1.3.2.1
1.2

I can't find a module.  Could you point me in the correct direction so that
I can read the fine manual?  I can't seem to find the right search term;
these are too general 'hierarchy', 'outline', 'number', 'sort'.

-- 
Michael R. Wolf
    All mammals learn by playing!
        MichaelRWolf at att.net