Leaving aside issues of language design and the emergence of other languages, it's interesting to think about other reasons why Perl lost popularity. Some of you know this history better than I do, but I think that it's now unknown to most HN readers.
The enormous reason that I see is the insistence, from Larry Wall and others, on a bottom-up "community" transition from Perl 5 to Perl 6. The design process for Perl 6 was announced at a Perl conference in 2000 [1]; 15 years later, almost every Perl user was still using Perl 5. The inability of the Perl community to push forward collectively in a timely way should be taken by every other language community as a cautionary tale.
Tim O'Reilly made a secondary point that may also be important. For a long time, Perl books were O'Reilly's biggest sellers. But the authors of those titles didn't act on his suggestion that they write a "Perl for the Web" book (really a Perl-for-CGI book). Books like that eventually came, but the refusal of leading authors to write such a book may have made it easier for PHP to get a foothold.
The enormous reason that I see is the insistence, from Larry Wall and others, on a bottom-up "community" transition from Perl 5 to Perl 6. The design process for Perl 6 was announced at a Perl conference in 2000 [1]; 15 years later, almost every Perl user was still using Perl 5. The inability of the Perl community to push forward collectively in a timely way should be taken by every other language community as a cautionary tale.
Tim O'Reilly made a secondary point that may also be important. For a long time, Perl books were O'Reilly's biggest sellers. But the authors of those titles didn't act on his suggestion that they write a "Perl for the Web" book (really a Perl-for-CGI book). Books like that eventually came, but the refusal of leading authors to write such a book may have made it easier for PHP to get a foothold.
[1] https://en.wikipedia.org/wiki/Raku_(programming_language)#Hi...