system will return the return code from the OS. This will be 0 if it is successful, thus a successful "move" will return a false value.

You want something like...

Die ("data load","YTSMSC","High","Could not move file: $filename for s
+uccessful exit: $@") if system("mv $filename $localpath/archives/");
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or more readable

system("mv $filename $localpath/archives/");
Die ("data load","YTSMSC","High","Could not move file: $filename for s
+uccessful exit: $@") if $?;
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