Linking expressions to central Controller

I'm trying to link up my expressions to one central Controller layer so that that one expression is shared across all objects in my project which require it.

I have "// Controller" composition with "Expression_Source (tK-logo_anim)" text layer. Its source text expression is set to my desired expression:

sourceLayer = comp("Killers logo (test)").layer("tK-logo_anim_mask");

sampleSize = [1,1];

samplePoint = transform.position;

color = sourceLayer.sampleImage(samplePoint,sampleSize);

x=color[0]*100;

[x,x]

Now, another composition includes a shape layer with its Transform Expression: Scale set to:

eval(comp("// Controller").layer("Expression_Source (tK-logo_anim)").text.sourceText.toString())

But when I try to hit enter on this line of code I get error: expression result must be of dimension 2, not 1

What am I doing incorrectly? The expression works when inserted manually into the Scale property but not when I try to link to it...

Thanks