Your script is probably using UTF-8 (as the encoding of the body of the script). So, you must

use utf8;
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I, personally (as a Brasilian that has pt_BR as native language), start all my scripts with:

use strict;
use warnings;
use utf8; # I will write this script in UTF-8
use open qw(:std :locale); # All files to be open in the native cp
use locale; # I want my string comparisons according to native locale
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This makes my I/O to be done in cp1252 in Windows, and in Latin1 or UTF-8 in linux. I edit my scripts in vim with UTF-8 encoding in both platforms.
Update:I recently learned that

use open qw(:std :locale);
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and

use open qw(:locale);
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do the same thing.