Malformed UTF-8 character

Stegalex has asked for the wisdom of the Perl Monks concerning the following question:

I just upgraded my server to RH Linux 8.0 with perl 5.8.0 and all of a sudden many of my "stable" scripts are producing the following message:

Malformed UTF-8 character (unexpected continuation byte 0x99, with no 
+preceding start byte) in substitution iterator at...".
[download]

It seems to happen in scripts where I am doing a

use Date::Manip qw(ParseDate UnixDate);
[download]

wherein I am only using parts of a module. Any ideas?

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