I ended up stripping the -d arg and using exec.

#!/usr/bin/perl -w  
BEGIN {
    # handle -d by itself to start the debugger
    @ARGV = grep { $_ eq '-d' ? !($opt_d=1) : 1 } @ARGV;
    exec('/usr/bin/perl','-dS',$0,@ARGV) if $opt_d;
}
...
[download]

Note that this doesn't do clustering like smarter switch process.

Also, I don't know if I need that -S but it's not hurting yet.