A combination of scancodekeypressed and a timer will achieve what you're looking for.
Example:
:state=0,scancodekeypressed=15:etimerstart,state=1
:state=1,scancodekeypressed=0:state=0
:state=1,etimergreater=1500:state=2
:state=2:[Do special stuff here]
When the user holds TAB (keycode 15) for 1.5 seconds it will move to state 2, where you can do whatever you needed. If they let go early, it will go back to state 0.
The one and only,
Only those who sow the seeds of their desires will reap their benefits later.
However, I have seeds of my own to tend to. I don't have time to be someone else's watering can.