I have wanted a right turn cornering light for my 1991 Mustang for several years.  Cadillacs have similar lights for both left and right turns as standard equipment. In my case the light illuminates an area I am turning into at night that is not adequately illuminated by the headlights.  The lamps are mounted in two holes in the right front plastic bumper shroud. Light is switched on when the right turn signal is activated. The pulse from the turn signal goes to a relay-capacitor-transistor circuit with a time constant of about 3 seconds so that the light stays on continuously during the turn and then extinguishes about 3 seconds after the turn signal stops.

I decided to use a somewhat unconventional scheme to wire and control the lights. The car is 30 years old and has lived in the Phoenix, Arizona area for as long. The heat in this locale tends to make the plastic electrical connectors brittle, and although I have the car's electrical schematics, I decided to not disturb these old connectors (and their plastic trim coverings) to make taps into the appropriate electrical wires. Instead, I sourced the needed signals directly from the headlight and turn lamp themselves, but  then to work properly,  these signals have to be processed by a custom made controller.