f(x) = @cond begin
    x < 0 => error("please provide a positive number")
    x < 5 => :smaller
    x == 5 => :equal
    x > 5 => :bigger
end

f(-5) # error!!
f(3) # :smaller
f(5) # :equal
f(7) # :bigger

f(x) =
    if x < 0
        error("please provide a positive number")
    elseif x < 5
        :smaller
    elseif x == 5
        :equal
    elseif x > 5
        :bigger
    else
        error("no match")
    end

f(x) =
    x < 0 ? error("please provide a positive number") :
    x < 5 ? :smaller :
    x == 5 ? :equal :
    x > 5 ? :bigger :
    error("no match")