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