How do I pass interpolation variables to AR validations?

(Rails 2.3.8)

Say I have in config/locales/en.yml:

en:
activerecord:
attributes:
foo:
bar: ‘Long%{br}name’

Now, in HTML I can do:
t(:‘activerecord.attributes.foo.bar’, :br => ‘
’)

and in LaTeX:
t(:‘activerecord.attributes.foo.bar’, :br => ‘\\’)

However, this is doomed to fail with AR validations, e.g.:

Model

class Foo < ActiveRecord::Base
validates_presence_of :bar
end

View Error

I18n::MissingInterpolationArgument in Foo#create
missing interpolation argument in “Long%{br}name” ({:count=>“1”} given)

So how do I pass :br to ‘activerecord.attributes.foo.bar’ in the context
of Foo?
Or is my approach wrong altogether?

Thank you

Got this working by using Ruby hashes instead of YAML:

{
:en => {
:activerecord => {
:attributes => {
:foo => {
:bar => lambda {|scope, opts| “Long#{opts[:br] || ’ '}name” }
}
}
}
}
}