Apparently, what touch(1) uses internally is utimensat(2). I haven't found anything on CPAN yet* that directly supports what you want to do, but in theory, you could use FFI::Platypus to link to it. Time::HiRes's utime does use utimensat, but doesn't support setting the AT_SYMLINK_NOFOLLOW flag needed to modify the symlink instead of the file it points to.

* Update: See here.