more documented
cosmetic change
lots of bugfixes
separate & rename
don't concat them
why destructive?
cosmetic change
why select?
just use String#[]
String#+ is evil.
Why didn't Dir::glob?
why didn't use .rb here but used later?
be more human readable
don't be too verbose
narrow down in advance
cosmetic change + debug info
use thread
Revert "use thread"

This reverts commit 86ba63219fab11d6794476dc393738f73496775c.
oops bugfix: require had to be inside rescue
local optimization that also makes code cleaner