give an example of reduction by HCl?

H2(g) + Cl2(g) -> 2HCl(l)
Here, in this reaction Chlorine has gained Hydrogen.

Therefore,
Chlorine is reduced(reduction).

We often hear of OXIDATION by HCl since it has H+ as the oxidizing agent (e.g. zinc is OXIDIZED BY dilute HCl(aq) to Zn2+).

When it comes to REDUCTION by HCl, it is still possible but only when reacting with an even stronger oxidizing agent.
Let's see one of those, a redox with (acidified) KMnO4 potassium permanganate:

Oxidation: 2Cl- --> Cl2 + 2e-
Reduction: MnO4- + 8H+ + 5e- --> Mn2+ + 4H2O
------------------------------------------------------------------------
Ionic: 10Cl- + 2MnO4- + 16H+ --> 5Cl2 + 2Mn2+ + 8H2O
Full : HCl + KMnO4 --> KCl + MnCl2 + Cl2 + H2O

Note that the species taking part in the redox, apart from MnO4-, is Cl- but NOT H+. It is a typical reaction to liberate chlorine gas with concentrated HCl and an O.A.
MnO4- is REDUCED BY HCl in this case.

Zn + HCl = ZnCl2 + H2