It was one way to do it. The goal was to keep @path with only "pure" node information

That's unrelated. I was referring to $#a=...; push @a,...;. The first statement sets the size of the array. Then next changes it. Why not just set it to the right size right from the start.

Me too. But a data structure outside the loop was needed to oversee things.

eh? What global data structure? I was referring $1 and $2. The only other global is DATA.