The regexp ^[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-[1-5][a-fA-F0-9]{3}-[89abAB][a-fA-F0-9]{3}-[a-fA-F0-9]{12}$ matches any valid UUID. This accepts v1, v2, v3, v4 and v5 UUIDs as FOLIO allows all of them, but it excludes the Nil UUID 00000000-0000-0000-0000-000000000000 that usually serves as a NullObject to be used for the Null Object Pattern.

A UUID has the form xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx where the version M must be [1-5] and the variant N must be [89abAB]

The shared raml-util repository has schemas/uuid.schema for UUID verification.

See also UUID at Wikipedia.