sort first two fields in numeric order

[Mark Lawrence]

I've got a file with tab separated columns of stuff that I
expand to pretty tabstops and sort.  I want to sort the file 
primarily on the first column and then on the second, both
numerically.  No problem, right?

expand -5 foo | sort +0n -1n 

should treat both the first and second columns as numerics
and sort them in that order.  It don't.  I get:

16  0
16  1
16  10
16  19
16  2
16  21

I'm missing something terribly obvious here.  Comments?
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mark at drd.com
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