Whatever is on the commandline will be used, if there's something there. If there's nothing on the commandline, the shell will look for the #! (she-bang) line and use that. So, the answer is Perl5.8.0.

I've run into this before in the other direction. I used to have V mapped to ":!perl %" in vi. I have 5.6.0 and 5.8.0 installed on my AIX box. When I needed to use 5.8.0, I have "#!/usr/bin/env perl5.8.0" as my she-bang line. But, my kepmap went to the 5.6.0 version, causing issues. (Cause DBD::Oracle going to Oracle9i only works for Perl5.8.0 on AIX.)