$ perl -E'say sprintf("%.100g", 0.15)'
0.14999999999999999
$ perl -E'say sprintf("%.100f", 0.15)'
0.14999999999999999444888487687421729788184165954589843750000000000000
+00000000000000000000000000000000
$ perl --version | head -3

This is perl 5, version 16, subversion 3 (v5.16.3) built for x86_64-li
+nux-thread-multi
(with 40 registered patches, see perl -V for more detail)
[download]

$ perl -E'say sprintf("%.100g", 0.15)'
0.1499999999999999944488848768742172978818416595458984375
$ perl -E'say sprintf("%.100f", 0.15)'
0.14999999999999999444888487687421729788184165954589843750000000000000
+00000000000000000000000000000000
$ perl -E'say sprintf("%.100a", 0.15)'
0x1.333333333333300000000000000000000000000000000000000000000000000000
+0000000000000000000000000000000000p-3
$ perl -v|head -3

This is perl 5, version 30, subversion 3 (v5.30.3) built for x86_64-li
+nux-thread-multi
(with 96 registered patches, see perl -V for more detail)
[download]

On my CentOS 7 box with perl-5.16.3

That's certainly one instance where you do benefit from formatting with "%.100f" instead of "%.100g".
Thank you for pointing this out.
Turns out that it's the same on my Ubuntu box with perl-5.18.0.
But with perl-5.32.0 on the same box, "%.100g" formatting works fine - so, there's a change in perl's behaviour between 5.18 and 5.32.
I would guess that "%.100g" formatting on your CentOS 7 box would also work fine on perl-5.32.

But I should point out that, even though "%.100g" formatting works ok on Ubuntu with perl-5.32.0, "%.*g" formatting is still buggy if you request a precision in the range 18..91 (inclusive).

$ perl -le 'printf "%.91f\n", 0.15;'
0.14999999999999999444888487687421729788184165954589843750000000000000
+00000000000000000000000
$ perl -le 'printf "%.91g\n", 0.15;'
0.14999999999999999
$ perl -le 'printf "%.92g\n", 0.15;'
0.1499999999999999944488848768742172978818416595458984375
[download]

Cheers,
Rob

No, it's simply an oversight.