That would be done exactly the way it is used to be.
You do still use digitalWrite(PINx, LOW/HIGH); to manipulate the PORT.
In general, this is a bad idea. What happens using this method if pinMode ever gets set to output? Poof goes the smoke.
If you insist on doing this, use the proper methods to guarantee the behavior so the pins never goes low-z.
Turn the LED on using: “pinMode(pin,INPUT_PULLUP);”
Turn the LED off with: “pinMode(pin,INPUT);”
Next, if you really want to win the most obfuscated code award, wrap the above in some #define macros so that the program can change from using internal to external pull-ups by changing defines rather than actual code.