And once more question:

In Czech, c followed by h is considered (for sorting etc.) as one 
character/grapheme ch. I need to split string to single characters with 
respect to this absurd manner.

In Perl I can write

split /(?<=(?![Cc][Hh]).)/, $string

and it works fine.

Unfortunately, Ruby does not implement/support this "zero-width positive 
look-behind assertion", so the question is how can one efficiently split 
the string in Ruby?

Thanks,

P.