ptest() was using this idea already.
As far as I can see, this is safe. Ttestsuite passes.
One downside is that a temporary from e.g. printf invocation
won't be freed until the next printf call.
function old new delta
awk_printf 481 468 -13
as_regex 137 111 -26
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(add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-39) Total: -39 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>