linebreaks in PL/pgSQL

I have written a small PL/pgSQL function. The error message is very long
and I wonder if there is a way to insert a linebreak into the code to
make it clearer: The code below makes a linebreak in the output as well:

...
BEGIN
IF (lower < 1) OR (higher < 1) THEN
RAISE EXCEPTION ''both param. have to be > 0'';
ELSE
IF (lower <= higher) THEN
lowtmp := lower - 1;
lowres := (lowtmp+1)*lowtmp/2;
highres := (higher+1)*higher/2;
result := highres-lowres;
ELSE
RAISE EXCEPTION ''The first value (%)
has to be higher
than the second value (%)'',
higher, lower;
END IF;
END IF;
RETURN result;
END;
...

Is there someting like that?
RAISE EXCEPTION ''The first value (%) has to be higher \
than the second value (%)'',
higher, lower;

(it doesn't lead to the desired result).

Hans

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