Here's a simpler version of choroba's idea:

#!/usr/bin/perl -l

use strict;
use warnings;

open my $in, "-|:encoding(UTF-8)", "echo \xc3\xb6" or die $!;

my $line = <$in>;
chomp($line);

open STDOUT, ">-" or die $!;
binmode STDOUT, ":encoding(UTF-8)";

print STDOUT "I read a line, that is ", length($line), " chars long.\n
+";
print STDOUT "That line in ascii is: $line";
close($in);
close(STDOUT);

exit 0;
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Updated: Fixed mistake at line 11. Thanks, choroba!