"Many thanks for your tips and advice."

You're very welcome.

"Unfortunately, installation of the latest stable version of Perl (v5.26.1) throws up the following error, when using the command $perlbrew install stable: ..."

I think you may have missed the beginning of the error message (perhaps where the text wrapped). What you posted begins with "or-strong ..."; I see on the next line "... -fstack-protector-strong ..."; maybe you've chopped off that first line in the middle of an option similar to that.

Further down, I see "clang: error: no such file or directory: 'lmm'". The line immediately before that ends with "... -lpthread -ldl lmm -lutil -lc": I'm wondering if "lmm" should really be "-lmm", which would match all the "-l*" parts surrounding it.

A search for the clang error didn't provide any useful results. I also had a look in "Active bugs for App-perlbrew": none of the "Subject" lines seemed relevant (although, they're not always as descriptive as they might be).

I don't normally use the "install stable" command; in fact, it's possible I've never used it. I typically have some non-default options, so I use a command with this format:

$ perlbrew install -v DOWNLOAD_URL -Dusethreads --as perl-5.x.xt
[download]

I get the DOWNLOAD_URL directly from the CPAN page (in the top-right corner you'll see "Download: link-to-tarball). So for 5.26.1, the link is http://search.cpan.org/CPAN/authors/id/S/SH/SHAY/perl-5.26.1.tar.gz, and the command would be:

$ perlbrew install -v http://search.cpan.org/CPAN/authors/id/S/SH/SHAY
+/perl-5.26.1.tar.gz -Dusethreads --as perl-5.26.1t
[download]

I haven't installed 5.26.1. The last one was 5.26.0, the link is http://search.cpan.org/CPAN/authors/id/X/XS/XSAWYERX/perl-5.26.0.tar.bz2, and the command I would have used was:

$ perlbrew install -v http://search.cpan.org/CPAN/authors/id/X/XS/XSAW
+YERX/perl-5.26.0.tar.bz2 -Dusethreads --as perl-5.26.0t
[download]

You can try either of those yourself. They both install Perl with thread support; if you don't want threads, omit the -Dusethreads, and leave off the "t" from the end of perl-5.x.xt (that's just my own convention to indicate threads).

I don't recall having any problems installing Perl using that method. I have successfully installed all of these:

$ perlbrew list
  perl-5.14.0t
  perl-5.14.2
  perl-5.14.2t
  perl-5.18.0t
  perl-5.18.1t
  perl-5.20.0t
  perl-5.20.2t
  perl-5.22.0t
  perl-5.24.0t
  perl-5.25.9t
* perl-5.26.0t
[download]