argathin has it right -- it's Red Hat's use of utf-8 by default. As you've noted, 'use bytes' fixes this within your script.

Another way around it is to unset the LANG environment variable (but for your script, you'd have to reinvoke with the new ENV setting). This is in case you're relying on external programs, such as the sort command, which sometimes break under the utf-8 setting.

Cheers,
Matt

P.S. By 'reinvoke', I mean something along the lines of this (ugly):

  #!/usr/bin/perl

  delete $ENV{LANG};
  exec($0, @ARGV);
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