I'm more inclined towards an {@ tag than a {# tag because the indentation could quickly get out of control

{#with someExpression as someVariable} <p>{someVariable}</p> {/with}

When the conditional part of an if-statement is long enough to require that it be written across multiple lines, it's worth noting that the combination of a two character keyword (i.e. if), plus a single space, plus an opening parenthesis creates a natural 4-space indent for the subsequent lines of the multiline conditional. This can produce a visual conflict with the indented suite of code nested inside the if-statement, which would also naturally be indented to 4 spaces.

The solution - move tabstops to fit the text between them and align them with matching tabstops on adjacent lines