I'm trying to write a regular expression that matches bencoded strings, 
i.e. strings on the form x:y, where x is the numeric length of y.

This is valid:

   6:foobar

while this is not:

   4:foo

I've tried using #{$1} inside the regexp, but it seems $1 is still nil 
at that point. Here's what I've got so far:

   /^([1-9]+\d*):(\w){#{$1}}$/

(it ain't working)

I'm matching with `string =~ regexp'; would it be better if I did it 
another way?


Cheers,
Daniel