regular expression positive look-behind
irb(main):001:0> input = " \t Jeffs "
=> " \t Jeffs "
SyntaxError: (irb):2: invalid pattern in look-behind: /(?<=\bJeff)(?=s\b)/
from E:/Ruby/Ruby193/bin/irb:12:in `'
This is a valid regular expression which should produce " \t Jeff's ". It seems to have a problem with the \b in the look-behind.