| SIGMA_BLOCK_EXISTS | Block '$block' already exists | Tried to add a block with a name that is already present in the template | Choose a different name for a new block | 
| SIGMA_PLACEHOLDER_NOT_FOUND | Variable placeholder '$placeholder' not found | There is no placeholder to replace by a new block in the template | Check the spelling of the placeholder name | 
| SIGMA_PLACEHOLDER_DUPLICATE | Placeholder '$placeholder' should be unique, found in multiple blocks | A placeholder to be replaced by a new block should appear only in one place | Check the spelling of the placeholder name, choose a different placeholder | 
| SIGMA_BLOCK_DUPLICATE | The name of a block must be unique within a template. Block 'blockname' found twice. | The added block contains a subblock that has the same name as the existing one | Check the $template and rename the block to something else | 
| 
           SIGMA_CALLBACK_SYNTAX_ERROR
          | 
           Cannot parse template function: (error description)
          | 
           Bogus syntax for template function parameters.
          | 
           Fix the template function definition, pay special attention to
           quoting rules.
          |