Heh ... I get the same output as you for @a, but for @b with use locale I get something different:

use locale: aaa aab aba abb Laa lab
[download]

Based on the @a output I would expect:

use locale: aaa aab aba abb lab Laa
[download]

which is different to what both you and I are getting. Someone here will probably understand what's happening ... not me, but.

Cheers,
Rob