{{!
    Welcome card:
    args:
        - tag
        - id
        - tail
!}}
{{#unless tag.is_match(r"^p|(h[1-6])$") && !id.is_empty() }}
   {{$ "Need static args: tag: str /^h[1-6]$/, id: str" }}
{{/unless }}
<{{ tag }} id="{{ id }}" class="welcome">Welcome{{ tail }}</{{ tag }}>