Constraints on Scalar Couplings from $\pi^\pm \to l^\pm\nu_l$

New interactions with Lorentz scalar structure, arising from physics beyond the standard model of electroweak interactions, will induce effective pseudoscalar interactions after renormalization by weak interaction loop corrections. Such induced pseudoscalar interactions are strongly constrained by data on $\pi^\pm \to l^\pm \nu_l$ decay. These limits on induced pseudoscalar interactions imply limits on the underlying fundamental scalar interactions that in many cases are substantially stronger than limits on scalar interactions from direct Beta-decay searches.