Custom field_error_proc

environment.rb

# Custom field_error_proc
ActionView::Base.field_error_proc = Proc.new do |html_tag, instance|
  errors = Array(instance.error_message).join(', ')
  if html_tag =~ /^<label/ 
    if html_tag !~ /^<label(?:\s+.*)*(\s+alt="(?:checkbox|hidden)")(?:\s+.*)*\s*/ 
        %(#{html_tag}).html_safe
    else  
        %(#{html_tag}<span class="validation-error">&nbsp;#{errors}</span>).html_safe
    end
  else  
    if html_tag =~ /(<input(?:\s+.*)*(\s+type="(?:checkbox|hidden)")(?:\s+.*)*\s*\/>)/ 
      %(#{html_tag}).html_safe
    else
      %(#{html_tag}<span class="validation-error">&nbsp;#{errors}</span>).html_safe
    end  
  end
end