Well, for starters, you need to address the syntactic errors in your code. When you're using strict, all the initial declarations of your variables need to start with my, eg. my $use_flock = 0;. Run your script with the -c argument to check for errors without actually executing the code, eg. perl -c guestbook.pl. If you don't understand the errors you get, use diagnostics will provide much more verbose error messages.

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DamnDirtyApe

Those who know that they are profound strive for clarity. Those who
would like to seem profound to the crowd strive for obscurity.
            --Friedrich Nietzsche