in reply to Perl, children and foreign languages
I did learn english myself at that age (through a dictionary and furious playing of the superb Infocom adventures), and I don't think that using an english programming language is too hard, as it will give your son the possibility to exercise english a bit more.
Having different language versions of one programming language in general is a very bad thing, as it breaks portability - I've seen a lot of Word macros break horribly when they were moved from a german copy of Word to a version with a different language.
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