Smart contract example: Crowdfunding contract pre-conditioned on variable UTXOs

UTXOs can be variables that must be conditionally enforced for the execution of a contract.

In this example, there is a conditional operation that executes a transfer of 100 USD from A to B conditioned on a set of variable UXTO transfers to A that each transfer [xi] USD with a policy that the sum of all [xi] must exceed 100 USD. This contract will require a signature from A on the operation.