Yes, if it isn't on CPAN then I usually won't try it and will strongly prefer an alternative (including rewriting it myself so that I can put it on CPAN).

but even then what assurance have you that CPAN will always be available when you need it?

Just a few days ago, someone told me that they couldn't install some module because CPAN had been down for a couple of days straight. My response was "What do you mean? CPAN is dozens of sites around the world. They all aren't down at the same time." And that is exactly why you should put your stuff on CPAN. (The problem was that their version of CPAN.pm was configured to only check one of these sites.)

Even if you happen to have a few dozen of your own public sites around the world, putting your stuff on CPAN will get it nicely indexed and searchable and everyone will know where to find it (I get so tired of seeing the "Where do I find..." questions about modules that aren't on CPAN).

As for software from the internet, for everything but CPAN I've been burned so whenever I download software I stow a copy in my "Masters" collection before installing it. This is difficult for some of the new things were you download a tiny program that "installs" the software by downloading the real software.

This practice is also helpful when you find yourself fixing things and eventually decide that you need to make a patch to send in. (:

        - tye (but my friends call me "Tye")