G-code

Hello,

I am trying to create my own custom g-code writer for 3d printing, and I first have a basic question which I hope someone can help me with - I would like to split a list of points based on their z value.  For example, I have contoured a shape at a desired height and I would like to separate each contour - is this possible? I was unsuccessful with the Sublist  & Member Index commands.  I have attached a sample definition.  Any help would be appreciated.

Something like this...

G1 X81.78 Y-5.38 Z40
G1 X81.79 Y-5.61 Z40
G1 X81.51 Y-6.21 Z40
G1 X81.41 Y-6.55 Z40
G1 X81.43 Y-6.8 Z40
G1 X81.3 Y-7.1 Z40
G1 X81.3 Y-7.1 Z41.25

G1 X82.53 Y0.06 Z41
G1 X82.46 Y1.68 Z41
G1 X82.27 Y3.2 Z41
G1 X81.93 Y4.75 Z41
G1 X81.46 Y6.22 Z41
G1 X81.13 Y7.05 Z41
G1 X80.71 Y7.95 Z41