Data::UUID guarantees that you won't get duplicates, ever.

While Data::UUID is a good solution, it doesn't guarantee that "you won't get duplicates, ever" (heck - there are only 128bits after all :-)

As the docs say...

A UUID is 128 bits long, and is guaranteed to be different from all other UUIDs/GUIDs generated until 3400 CE.

...

It provides reasonably efficient and reliable framework for generating UUIDs and supports fairly high allocation rates -- 10 million per second per machine -- and therefore is suitable for identifying both extremely short-lived and very persistent objects on a given system as well as across the network.

So, it wouldn't be suitable if you were coding something up for The Long Foundation - or needed to allocate UUIDs really, really, really quickly :-)

The full gory detail can be found in this IETF draft.

All this complexity is, of course, why I like Data::UUID. People who are experts have taken the time to look hard at the algorithm, and I can have some confidence in it working well.

In reply to Re^2: MD5-based Unique Session ID Generator by adrianh
in thread MD5-based Unique Session ID Generator by radiantmatrix

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