I always put the she-bang line in, if only because it lets
my editor know it's a Perl program. Furthermore, it allows
you to put arguments to perl itself there - although since
we have 5.6, I don't do it so often anymore. I used to put
-w on the shebang line, but now we have lexical warnings.
-T still goes there, for the few programs I write that need
it. Every now and then I put -l or -p/-n there, but that's
fairly uncommon.
Having said that, even with a she bang line, I sometimes
do perl program args. Typically if the program
doesn't have the execute bit set yet. Or if I cut-and-pasted
a program from perlmonks or comp.lang.perl.misc
that doesn't have a she-bang line, or has a she-bang line
not pointing to a perl on my machine.
Abigail