I agree. My post was mainly intended to demonstrate the use of %n as you'd requested. It was not a recommendation for production-grade code.
I would probably just generate the potentially long string with sprintf("%.2f %d/%d/%d %s", @$record); then use printf to truncate and print. You have a number of options here; I've shown a selection below — the first pair indicates a gotcha which you should avoid; the remaining three pairs are all potential candidates (depends on the final output you want).
$ perl -e ' my $x = "12345"; my $y = "1234567890"; printf q{%-*2$s|}."\n", $x, 9; printf q{%-*2$s|}."\n", $y, 9; printf q{%-.*2$s|}."\n", $x, 9; printf q{%-.*2$s|}."\n", $y, 9; printf q{%-*2$.*2$s|}."\n", $x, 9; printf q{%-*2$.*2$s|}."\n", $y, 9; printf q{%-*2$.*3$s|}."\n", $x, 10, 9; printf q{%-*2$.*3$s|}."\n", $y, 10, 9; ' 12345 | 1234567890| 12345| 123456789| 12345 | 123456789| 12345 | 123456789 |
The (possibly odd-looking) 'q{...}."\n"' is needed to avoid a 'Global symbol "$s" requires explicit package name ...' error. You could escape the '$' signs (e.g. "%-*2\$.*3\$s|\n") but, in my opinion, that makes the already somewhat cryptic format even less readable.
I hadn't previously used '%n', so that was an interesting learning exercise for me. Thanks for the question.
— Ken
In reply to Re^3: How to use sprintf %n formatting pattern
by kcott
in thread How to use sprintf %n formatting pattern
by ibm1620
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