Revise minimum perl requirement

[skaji]

Currently cpm targets Perl 5.8.1 according to The Lancaster Consensus.

Now it has been obsoleted by The Lyon Amendment,
which states that the Perl toolchain will target v5.16 in 2023, v5.20 in 2024, v5.22 in 2025, and so on.

This is a good opportunity to revise minimum perl requirement for cpm. There are 3 options:

• option1: v5.16.0
  • Follow The Lyon Amendment. Technically, cpm treats v5.8, v5.10 as special because of @INC order. If we bump Perl requirement to v5.16.0, then I can eliminate this special stuff.
• option2: v5.8.1
  • cpm supports v5.8.1 already, so I don't think it's very difficult to continue to support v5.8.1 as long as other toolchain supports v5.8.1. But I'm not sure how many people still use v5.8 on a daily basis.
• option3: v5.10.1
  • RHEL6 comes with Perl v5.10.1. So it might be still worth supporting v5.10.1.

I think I want to choose option1, v5.16.0.
What do you think?

[skaji]

Now Module::Build::Tiny requires perl v5.10:

❯ perl -v
This is perl, v5.8.9 built for darwin-2level

❯ curl -fsSL https://cpanmin.us | perl - -nq Module::Build::Tiny
Successfully installed ExtUtils-MakeMaker-7.70 (upgraded from 6.48)
Successfully installed Test-Harness-3.48
Successfully installed version-0.9932
Successfully installed Module-Metadata-1.000038
Successfully installed Locale-Maketext-Simple-0.21
Successfully installed Test-Simple-1.302199 (upgraded from 0.80)
Successfully installed Module-Load-0.36
Successfully installed Module-CoreList-5.20240420 (upgraded from 2.17)
Successfully installed Params-Check-0.38
Successfully installed Module-Load-Conditional-0.74
Successfully installed IPC-Cmd-1.04
! Installing the dependencies failed: Your Perl (5.008009) is not in the range 'v5.10.0'
! Bailing out the installation for CPAN-Meta-Requirements-2.143.
Successfully installed ExtUtils-Config-0.009
Successfully installed ExtUtils-HasCompiler-0.024
Successfully installed Perl-OSType-1.010
! Installing the dependencies failed: Module 'CPAN::Meta::Requirements::Range' is not installed
! Bailing out the installation for CPAN-Requirements-Dynamic-0.001.
Successfully installed JSON-PP-4.16 (upgraded from 2.27203)
Successfully installed CPAN-Meta-2.150010 (upgraded from 2.143240)
Successfully installed ExtUtils-CBuilder-0.280236
Successfully installed ExtUtils-Helpers-0.026
Successfully installed ExtUtils-InstallPaths-0.013
! Installing the dependencies failed: Module 'CPAN::Requirements::Dynamic' is not installed
! Bailing out the installation for Module-Build-Tiny-0.048.
19 distributions installed

❯ echo $?
1