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