$ perl -E'say sprintf("%.100g", 0.15)'
0.14999999999999999
$ perl -E'say sprintf("%.100f", 0.15)'
0.1499999999999999944488848768742172978818416595458984375000000000000000000000000000000000000000000000
$ perl --version | head -3

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

##</code><code>##

$ perl -E'say sprintf("%.100g", 0.15)'
0.1499999999999999944488848768742172978818416595458984375
$ perl -E'say sprintf("%.100f", 0.15)'
0.1499999999999999944488848768742172978818416595458984375000000000000000000000000000000000000000000000
$ perl -E'say sprintf("%.100a", 0.15)'
0x1.3333333333333000000000000000000000000000000000000000000000000000000000000000000000000000000000000000p-3
$ perl -v|head -3

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