Techniques for flow-based scoping are disclosed. A first code segment in a sequence of same-level code segments encapsulates a first lower-level lexical scope. The first lower-level scope is inclusive of scoping provided for the sequence of same-level code segments. The first code segment comprises a condition and an uninitialized variable. If executed, the first code segment causes the condition to be evaluated. If the condition is satisfied, the uninitialized variable is initialized and made available only within the first lower-level lexical scope. If a second code segment (a) references the uninitialized variable and (b) is in the sequence of same-level code segments or in a second lower-level lexical scope outside of the first lower-level lexical scope, an error message is presented indicating that the uninitialized variable is out of scope for the second code segment.