because the autovivified element has no value. it is being created though as you can see by adding...

use Data::Dumper;
print Dumper($hashref);

# or even just

print 'success' if exists $hashref->{foo}{foo};
[download]

additionally, if you put use diagnostics; at the top of your script you will get extended warnings which may help.

   larryk                                          
perl -le "s,,reverse killer,e,y,rifle,lycra,,print"