I added several methods, and options, and reworked the guts into a more extendable core.

added options to new():
sep_string - specify the separator that
defines a "line", defaults to $/.
recycle - causes randomline and randomlines
to reload the index (quickly, by
copying the line based index)

new methods:
length - returns the number of lines left
for randomline and randomlines
r_eof? - returns true if randomline(s) is
out of lines.
randomlines(x) - returns x random lines.

more tests were added as well.