Are you sure the issue is not something magical about the PCs after the first one? There are a couple of interesting coding techniques, but nothing that would cause the symptoms described and nothing that ought be affected by different minor versions of Perl.

The @ARGV issue also sounds much more likely to be the way your script is being run than a Perl issue. Try writing a trivial script that just echos @ARGV and run that in the same context as your troublesome script. Something like:

print "@ARGV";
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As for the coding foibles: rather than /\.PST$/ || /\.pst$/ you could consider /\.PST$/i which performs a case insensitive match.

There is no need to concatenate sections of strings together. Just use a single string:

my $entry = "$PCName    $File::Find::dir/$_\n";
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To concatenate a string on to the end of a variable you can:

$entry .= " = $size bytes\n";
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