We use the shebang line, except when testing. 90% of the Perl programs we use are set in the crontab, so that would get ugly if we had to add "perl /path/to/program" everytime :-). If I'm testing at the commandline, I might type "perl program.pl" or not, depending on my mood. But definitly if I want it to run in debug mode the first time or two.
"Ex libris un peut de tout"