# File lib/rake.rb, line 77
77:     def ext(newext='')
78:       return self.dup if ['.', '..'].include? self
79:       if newext != ''
80:         newext = (newext =~ /^\./) ? newext : ("." + newext)
81:       end
82:       dup.sub!(%r(([^/\\])\.[^./\\]*$)) { $1 + newext } || self + newext
83:     end