[HTTPS-Everywhere] In Google.xml, why "[^/@:]"?

[Osama Khalid]

In Google.xml and GoogleServices.xml, "[^/@:]" is used to match
language codes. Language codes[0] consists of two letters. Numbers and
other spacial characters are not included.

I wonder if we should use the standard '[a-zA-Z]' to match all
letters and to avoid catching misspelled URLs.

[0]: http://en.wikipedia.org/wiki/List_of_ISO_639-2_codes

--Osama Khalid