Hi,

"What does it do?"

Nothing you can't do with other syntax, as shown by this one-liner which reproduces the output documented for -nest in the old version choroba linked to here.

$ perl -Mstrict -MSQL::Abstract -wE 'say +(SQL::Abstract->new->select(
+"foo", "bar", { user => "nwiger", -or => [ workhrs => { ">" => 20 }, 
+geo => "Asia" ]}))[0]'
[download]

SELECT bar FROM foo WHERE ( ( workhrs > ? OR geo = ? ) AND user = ? )
[download]

Hope this helps!