@condition:

0-without @condition:.hs

if: a?
    then: { a }
    else: {
        if: b?
            then: { b }
            else: { c }
    }

1-with @condition:.hs

condition: {
    a? -> a
    b? -> b
    otherwise -> c
}

2-@condition:.hs

condition: (b: Block) :=
    if: b contents empty?
        then: { raise: "condition: no branches are true" }
        else: {
            es = b contents
            [c, e] = es head targets

            check = c evaluate-in: b context
            if: check
                then: { e evaluate-in: b context }
                else: { condition: (Block new: es tail in: b context) }
        }

otherwise := True

3-real-world example.hs

-- from:
    if: h tag empty?
        then: { c }
        else: {
            if: (c empty? && (Self-Closing contains?: h tag))
                then: { "<" .. h tag .. attrs .. " />" }
                else: {
                    "<" .. h tag .. attrs .. ">" .. c .. "</" .. h tag .. ">"
                }
        }

-- to:
    condition: {
        h tag empty? -> c

        c empty? && (Self-Closing contains?: h tag) ->
            "<" .. h tag .. attrs .. " />"

        otherwise ->
            "<" .. h tag .. attrs .. ">" .. c .. "</" .. h tag .. ">"
    }