lassign

lassign <list> <variable 1> <variable 2> ...

# Assign the first three elements on the list to variables
# x, y, and z
lassign [get_cells *~FF] x y z ]
set pins_on_x [get_pins $x]
set pins_on_y [get_pins $y]
set pins_on_z [get_pins $z]