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The infinite real integral exists for the same reason as before: we still have $|\exp(-2it)| = 1$ for all real $t$. However, in this case we would define $f : \C \setminus \{i,-i\} \to \C$ by $f(z) = \dfrac{\exp(-2iz)}{z^2 + 1}$ and would be stuck with \[ |\exp(-2iz)| = \exp(2y) \] in the numerator. This term grows quickly as $y \to \infty$ so we would not be able to control the semi-circular contour integral.
We can instead use $\nu(t) = T e^{-it}$ on $[0,\pi]$ to get from $T$ to $-T$. Indeed, since \[ |\exp(-2iz)| = |\exp(-2ix) \exp(2y)| = \exp(2y) = e^{-2|y|} \] when $y \l 0$, going below the horizontal axis lets us regain control of our semi-circular contour integral. We need to be a bit careful with Cauchy's residue theorem as well. It says \[ \int\limits_{-\infty}^\infty \dfrac{\exp(-2it)}{t^2 + 1} \intd t = 2 \pi i \wind(\Gamma,-i) \Res(f,-i) \] because our contour $\Gamma = (\gamma,\eta)$ now contains $-i$ and not $i$, and winds clockwise around $-i$ i.e.\ $\wind(\Gamma,-i) = -1$. So \[ \int\limits_{-\infty}^\infty \dfrac{\exp(-2it)}{t^2 + 1} \intd t = 2 \pi i (-1) \dfrac{\exp(-2i \cdot (-i))}{2(-i)} = \dfrac{\pi}{e^2} \]