Use some combination of the current date/time, a random number, and possibly a checksum to improve validity. Eg: 
my $uniqueId = time()*10000 + int rand (10000);
$uniqueId = $uniqueId*100 + ( 
   ( ( $uniqueId div 10000000) % 10 ) * 
   ( ( $uniqueId div 100 ) % 10 ) );

[download]
The latter uses the 8th and 3rd digit from the right as checksums in this case.
Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain

In reply to Re: Random, Unique, but Simple session ID by Masem
in thread Random, Unique, but Simple session ID by akm2

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