and stops at 'za'

Stops at 'aa', actually

$ perl -le'print ++($_="z")'
aa

$ perl -le'$,=" "; print "e".."d"'
e f g h i j k l m n o p q r s t u v w x y z

$ perl -le'$,=" "; print "e".."za"'
e f g h i j k l m n o p q r s t u v w x y z aa ab ...[647]... yz za
[download]

perlop goes on to say:

But doesn't that feel like it's documenting a bug?