How can I use a variable in "Sort" or "Filter" function in EKL?

Hello,

For examble,lst1 is a list full of point and there is a p1 as a variable.I'd like to rearrange lst1 according to the distance to p1.I write a sentence as "lst2=lst1.Sort("<","point","length","y=distance(x,p1)")".But EKL can't recognize p1 as a variable.How can I make it?