in reply to Re^2: Dereferencing undef as an array: Bug or WAD?
in thread Dereferencing undef as an array: Bug or WAD?

It does persist—you've autovivified $r as a reference to an array, but that array is still empty:

% perl -Mstrict -wle 'my $r = undef; map ++$_, @$r; print $r;' ARRAY(0x10116180)