[plt-scheme] string->symbol and case

Hi,
I'm trying to eval symbols that I get with (string->symbol str) :

> (define AA 'hi)
> (string->symbol "AA")
|AA|

so...
> (eval (string->symbol "AA"))
reference to undefined identifier: AA

It seems that eval doesnt removes quoting vertical bars so I cant run it.
Is this a case insensitive problem ? How can I make my capital letters string 
eval the same name function ?
Thanks