  It is shown that, in QCD, the same universal function
$\Gamma_{cusp}(\vartheta, \alpha_\s)$ determines the infrared behaviour of the
on-shell quark form factor, the velocity-dependent anomalous dimension in the
heavy quark effective field theory (HQET) and the renormalization properties of
the vacuum averaged Wilson lines with a cusp. It is demonstrated that a
combined use of the methods developed in the relevant different branches of
quantum field theory essentially facilitates the all-order study of the
asymptotic and analytic properties of this function.
