You could change the distribution of @mirrors like this

my @mirrors;

push @mirrors, 'http://foo.mirror.org'                   for 1..3;
push @mirrors, 'http://www.users-domain.com/proj/foo'    for 1..2;
push @mirrors, 'http://osdn.dl.sf.net/sourceforge/foo'   for 1..3;
push @mirrors, 'http://unc.dl.sf.net/sourceforge/foo'    for 1..4;
push @mirrors, 'http://umn.dl.sf.net/sourceforge/foo'    for 1..4;
push @mirrors, 'http://heanet.dl.sf.net/sourceforge/foo' for 1..5;
push @mirrors, 'http://aleron.dl.sf.net/sourceforge/foo' for 1..5;

print $cgi->a({-href  =>
       "$mirrors[int(rand(@mirrors))]/$file-$stable.rpm",
               -title =>"$stable RPM"}, 'rpm');
[download]