Alternately, it's not at all difficult to write keystroke macros that do things like "insert a '#' in front of this line and then move down one line", which you can loop to comment a series of lines.
The default keystrokes for that (Off the top of my head, and untested):
Defining the macro:
Running it once:C-x ( C-a # C-n C-x )
Running it 10 times:C-x e
C-u 10 C-x e
My personal preference: don't use one of the workarounds. Everyone understands "#" commented lines, but many will find your workaround confusing. Optimize for readability, not for ease of typing.
But if you do use a workaround, my preference would be for abusing pod ('=for comment/=cut'), which is endorsed by Damien Conway in "Perl Best Practices".