[TriLUG] vi or sed or perl question - joining lines

[Mike Norwood]

Hello,

I have a big goofy text file I need to get into a more usable format.  
Basically what I need to do is join every 12 lines into 1 line, down 
through the entire file.  Does anyone have a good suggestion on how to do 
this?  I know that I must have done this same thing 2 years ago, because I 
found an earlier version of this same data from May 2005 that I somehow 
converted, but I now have no idea how it was done.

Thanks, Mike