Interview with Donald Knuth (InformIT)

There is a difference between reuseable and editable.  Reuseable code has to be so thoroughly
documented that you never need to look inside it to know exactly what happens under corner
cases.  I have run into this problem so often that I feel, like Knuth, that editable source is
better.  Perl's LWP is a great example.  I love it, it usually does just what I want, but then
there are conditions where I don't know what it does, and I have to inspect the source or poke
around in the debugger to find out exactly what is going on.  If it were closed, I would be
stuck.  If it were proprietary but with source available, like Microsoft's useless "shared
source", I would still be stuck if it didn't do the right thing or had a bug.