conditional if

$if{expr} … $elif{expr} … $else … $fi

The conditional if/elif/else construct,
apart from the closing $fi,
behaves just like you would expect i.e. as in python,
with optional (multiple) $elif{}‘s and an optional
concluding $else.

The condition expression may be any python expression, that
must evaluate without errors in the supplied namespace.
As for all directives, being on a single line or spanning
many lines has no relevance.