Faster perl operation?

[Kevin Brown]

I'm working on a small script (so far only about 1000 lines long) and 
I'm finding that I'd like a faster way to do:

$variable = "." x ($start - 1);

which is incredibly slow since it is creating sometimes on the order of 
100,000 to 3,000,000 (yes, Million) periods to fill up the needed string.

I've tried using:
sprintf +("%s" x ($start - 1)), ".";

but I must not have the syntax correct as it doesn't create the needed 
"." characters.

Any thoughts on what is wrong with the sprintf syntax or what else I 
could try to speed this up?