Having no experience with this, I thought I would explore a bit. So I did the following:

#!/usr/bin/perl
use strict;
use warnings;

use open IO => ':utf8';

while(<DATA>) {
  chomp;
  (my $nonenglish = $_) =~ s/[A-Za-z]//g;
  my @chars = split(//,$nonenglish);
  my $chars = scalar(@chars);
  print scalar(@chars), " $nonenglish\n";
}

__DATA__
æ
æð
æða
æðaber
æðahnútur
æðakölkun
æðardúnn
æðarfugl
æðarkolla
æðarkóngur
æðarvarp
æði
æðimargur
æðisgenginn
æðiskast
æðislegur
æðrast
æðri
æðrulaus
æðruleysi
æðruorð
æðrutónn
æðstur
æður
æfa
__END__
[download]

Seems split sees those letters as two chars also, which makes sense now that I think of it... . Guess I have some things to learn about UTF8!
Thanks for the opportunity! Sorry this is not all that helpful. Suppose one could take the character count and just divide by two ...

$chars = $chars / 2;
print "$chars $nonenglish\n";
[download]

...

Update: Might also take a look at CPAN Test UTF8 and related...