Perturb_dipole ? to change electric filed applied for a moleclue

I’m interested in how the polarization change depending on the electric field where the unit is, for instance, volt per meter (V/m).

I chekced the past posts, and found that some uses perturb_h , perturb_dipole, etc. However, I’m not sure how perturb_h , perturb_dipole relate to electric field.

Would someone do teach me about this point?

psi4/tests/props1/input.dat at master · psi4/psi4 · GitHub might help.

Thank you for the comment.

set perturb_dipole [0, 0, $l]
Is this electric field that one want to apply for?
Where can I check the unit of the field?
Best regards