format string does not work with Ruby < 1.9.0-2

[takuo]

IMAProwl/1.2.0's Format string does not work with old Ruby 1.9.0

on Debian lenny.
% ruby -v
ruby 1.9.0 (2008-06-20 revision 17482) [i486-linux]
% ruby1.9 -e '"p %{a}" % { :a=>"word" }'
-e:1:in %': malformed format string - %{ (ArgumentError) from -e:1:in

'

on Debian sid
% ruby1.9 -v
ruby 1.9.0 (2008-10-04 revision 19669) [i486-linux]
% ruby1.9 -e 'p "%{a}" % { :a=>"word" }'
"word"