  Decays $D\to\pi^+\pi^-e^+\nu_e$ and $D_s\to\pi^+ \pi^-e^+\nu_e$ serve as
probes that check the existence of constituent $q\bar q$ components in the wave
functions of scalar mesons decaying into $\pi^+\pi^-$. There exists a great
deal of concrete evidence in favor of the exotic four-quark nature of light
scalars. At the same time, the further expansion of the area of the $q^2\bar
q^2$ model validity for light scalars on ever new processes seems extremely
interesting and important. We analyze the BESIII and CLEO data on the decays
$D^+\to \pi^+\pi^- e^+\nu_e$ and $D^+_s\to \pi^+\pi^- e^+\nu_e$ and show that
the results of these experiments together can be interpreted in favor of the
four-quark nature of light scalar mesons $\sigma(500)$ and $f_0(980)$. Our
approach can also be applied to the description of other similar decays
involving light scalars.
