The major modern use case I know of is command-line utilities which also benefit from low start-up. Of course, that doesn't mean there hasn't been "perf rot" over the decades as you say. Such rot should never surprise anyone. :-)
Some perl5 lover should take the time to compile all those 5.6 to 5.42 versions on the same host OS/CPU and do a performance comparison and create a nice chart for the world to trap and maybe correct such performance regressions. I just tried getting 5.8.9 to compile on modern Linux with gcc-15, and it seemed like a real PITA. (Earlier didn't even ./Configure -des right.)
Well, I spent a little more time on it, and for that one Perl version (on one cpu, i7-6700k, one OS - Linux 6.15, with one compiler gcc-15) I got a 1.5x slowdown of perl startup from 2008 to 2025. Not great!
zsh# rei=(chrt 99 taskset -c 2-3 env -i HOME=$HOME PATH=/bin)
zsh# tim=(-k2 -o14 -n14 -m14)
# Set 1
zsh# $rei tim $tim './perl-5.8.9</n' 'perl-5.42.0</n'
218.5 +- 1.9 μs (AlreadySubtracted)Overhead
626 +- 14 μs ./perl-5.8.9</n
953.5 +- 8.6 μs perl-5.42.0</n
# Set 2
zsh# $rei tim $tim './perl-5.8.9</n' 'perl-5.42.0</n'
247 +- 15 μs (AlreadySubtracted)Overhead
633 +- 26 μs ./perl-5.8.9</n
989 +- 25 μs perl-5.42.0</n
# Consistency check - well within 2 sigma for both
zsh# a (989 +- 25)-(953.5 +- 8.6)
36 +- 26
zsh# a (626 +- 14)-(633 +- 26)
-7 +- 30
# Final report; weighted means to maximize precision
zsh# a mean(989 +- 25,953.5 +- 8.6)/mean(626 +- 14,633 +- 26)
1.525 +- 0.033
EDIT: Oh, yeah, and /n -> /dev/null is a symlink I always use.
Some perl5 lover should take the time to compile all those 5.6 to 5.42 versions on the same host OS/CPU and do a performance comparison and create a nice chart for the world to trap and maybe correct such performance regressions. I just tried getting 5.8.9 to compile on modern Linux with gcc-15, and it seemed like a real PITA. (Earlier didn't even ./Configure -des right.)