Fetch file -- use axel or prozilla instead of curl

I find file fetch is fairly slow esp. for sites like sf.net. port always chooses mirror easynews which is slow for me and prone of timeout. I checked /usr/local/share/darwinports/Tcl/port1.0/portfetch.tcl (I use /usr/local instead of /opt/local) and find file fetch uses curl. Since I installed and tested axel, I find it's fairly good, about as fast as prozilla (I have experience of using Gentoo which uses prozilla). My question is how to hack portfetch.tcl to use axel instead. Sure simply change curl to axel does not work. Wish someone can help me. Thanks.