$ perl -MO=Deparse -e '@bar ||= (1,2,3)'
Can't modify array dereference in logical or assignment (||=) at -e line 1, at EOF
-e had compilation errors.
@bar ||= ('???', '???', 3);

$ perl -MO=Deparse -we '@foo ||= 1'
Can't modify array dereference in logical or assignment (||=) at -e line 1, at EOF
-e had compilation errors.
BEGIN { $^W = 1; }
@foo ||= 1;