  We introduce a new, demand-driven variant of Spector's bar recursion in the
spirit of the Berardi-Bezem-Coquand functional. The recursion takes place over
finite partial functions $u$, where the control parameter $\varphi$, used in
Spector's bar recursion to terminate the computation at sequences $s$
satisfying $\varphi(\hat{s})<|s|$, now acts as a guide for deciding exactly
where to make bar recursive updates, terminating the computation whenever
$\varphi(\hat{u})\in\mbox{dom}(u)$. We begin by exploring theoretical aspects
of this new form of recursion, then in the main part of the paper we show that
demand-driven bar recursion can be directly used to give an alternative
functional interpretation of classical countable choice. We provide a short
case study as an illustration, in which we extract a new bar recursive program
from the proof that there is no injection from $\mathbb{N}\to\mathbb{N}$ to
$\mathbb{N}$, and compare this to the program that would be obtained using
Spector's original variant. We conclude by formally establishing that our new
bar recursor is primitive recursively equivalent to the original Spector bar
recursion, and thus defines the same class of functionals when added to
G\"odel's system $\sf T$.
