The problem is not so much setting up the pipes on the Perl side, but rather getting the other side (svg2pdf in this case) to communicate via the pipes, if it expects to do its IO solely via named files instead of stdin/stdout — as svg2pdf apparently does, according to the OP.

IO::Pipe won't really help in this regard. as it sets up normal anonymous pipes, and those can only be used if the subprocess on the other end cooperates.