The SHL and SHR operators were from @zebra - he could best speak to use cases (my imagination is failing me at the moment for some reason).
The operators implement bit shifting:
The A input is the value to be shifted while B is the number of bits to shift A by. Like many of the other operators setting A outputs the shifted A immediately, setting B just performs the shift (no output unless TRIG is set > 0).
SHL shifts bits left, SHR shifts bits right.