How about something like this:
You can vary the number of iterations (1..5) and
scaling factor (20) based on the exact
distribution curve you want.
There are several other ways to approach this
problem. If efficiency were of paramount importance,
I would try using statistical method to derive
a function that would aproximate the curve of
how in frequency you would map numbers from 0 to 0.9999 (the range of perl's rand function)
into the range you want (1 to 100).