  Fluctuations in Lyman-$\alpha$ (Ly$\alpha$) forest transmission towards
high-$z$ quasars are partially sourced from spatial fluctuations in the
ultraviolet background (UVB), the level of which are set by the mean free path
of ionizing photons ($\lambda_{\text{mfp}}$). The auto-correlation function of
Ly$\alpha$ forest flux characterizes the strength and scale of transmission
fluctuations and, as we show, is thus sensitive to $\lambda_{\text{mfp}}$.
Recent measurements at $z \sim 6$ suggest a rapid evolution of
$\lambda_{\text{mfp}}$ at $z>5.0$ which would leave a signature in the
evolution of the auto-correlation function. For this forecast, we model mock
Ly$\alpha$ forest data with properties similar to the XQR-30 extended data set
at $5.4 \leq z \leq 6.0$. At each $z$ we investigate 100 mock data sets and an
ideal case where mock data matches model values of the auto-correlation
function. For ideal data with $\lambda_{\text{mfp}}=9.0$ cMpc at $z=6.0$, we
recover $\lambda_{\text{mfp}}=12^{+6}_{-3}$ cMpc. This precision is comparable
to direct measurements of $\lambda_{\text{mfp}}$ from the stacking of quasar
spectra beyond the Lyman limit. Hypothetical high-resolution data leads to a
$\sim40\%$ reduction in the error bars over all $z$. The distribution of mock
values of the auto-correlation function in this work is highly non-Gaussian for
high-$z$, which should caution work with other statistics of the high-$z$
Ly$\alpha$ forest against making this assumption. We use a rigorous statistical
method to pass an inference test, however future work on non-Gaussian methods
will enable higher precision measurements.
