There may be another way:

#!/usr/bin/env perl
[download]

That is not ideal. It still involves updating all those scripts (but at least the update is a simple and constant string replacment). It puts the load on managing how the PATH, PERLLIB, PERL5LIB (and other?) shell variables are set for every user at every machine (but you might need at most half a dozen distinct settings, depending on how many distinct perl builds are needed).

And of course, whenever you bring in a script that some else has written (e.g., as posted at PerlMonks), you'll probably need to edit the shebang line -- but I gather you might be doing this already.