http://www.perlmonks.org?node_id=1010291


in reply to Re^2: The Perl 6 Coding Contest 2012
in thread The Perl 6 Coding Contest 2012

Yep, moritz has it right.

Think of it like this. The fundamental operation is "exchange wires N and N+1". This is depicted graphically with a single crossing between two adjacent wires. You're allowed to put several of these fundamental operations in the same column, provided no two operations in the same column act on the same wire.