There are many languages still in use today that have all kinds of warts and ugliness, but they remain in use because they still have momentum and lots of legacy things built in them. So being ugly or old isn’t enough of a factor for people to abandon something in droves.
Once you need to rewrite everything, there’s no reason to stay with something you know since you need to fully retool anyway.
As a Perl programmer since v5 was released, the confusion around 6 completely destroyed almost everyone’s enthusiasm, and immediately caused all new projects to avoid Perl. It seemed like 5 had reached the end of the line, and 6 was nowhere to be found. Nobody wants to gamble so many hours of their lives, and the future of their business, on such an uncertain environment.
If Perl 6 had any visible movement within the first few years, it might have survived, but it was a good decade before they even admitted Perl 6 might take longer than expected, and then more time after that before they admitted it should have been a new language. 6 was interesting for language geeks, and they probably did some cool things, but you can’t run a large popular project like it’s a small research project. That completely destroyed all momentum in the community. Perl 5 development only resumed far too late, after the writing was already on the wall.
Both Bill Gates and Linus understand backwards compatibility as a sacrosanct principle. Python only just barely survived the jump from 2 to 3. JavaScript can only survive this because there’s no other option in a browser.
I learned Python from reading a pocket language reference that just described the syntax and standard library, because the language was simple and easy to understand and everything made sense.
Conversely, I was trying to debug a script someone else ran and came across a line that said '$|++'; it was impossible to search for on the web, and when I asked on IRC the only answer I got was 'man perldoc' which also did not answer my question in any reasonable way.
For anyone wondering: `$|` is an alias for `$OUTPUT_AUTOFLUSH`; it defaults to 0 (line-buffered) but any non-zero value means 'flush output immediately'. Thus '$|++' changes 0 to 1 (or 1 to 2, etc), which means that '$|++' means 'turn off output buffering'. No one could be bothered to say that; if you had questions about the language you clearly didn't RTFM well enough so that became the default/only answer I ever saw.
Meanwhile, the PHP community was often welcoming and helpful to newcomers, despite most of them being bad at programming and giving bad advice, and the Python community produced a language that was so often self-explanatory that new user questions were more about how Python did things or asking about how to implement things they didn't realize were in the standard library.
So yeah, lots of things contributed to Perl's decline, but the community being a bunch of elitist toxic dicks sure didn't help matters and it meant that as the set of people looking to learn how to do programming on Linux grew past the neckbeards looking for any metric to show that they were better than other people then Perl's growth potential was finite.
Your overall point notwithstanding, this was just bad advice. What you want is `man perlvar` (or equivalently `perldoc perlvar`) which documents this and other predefined variables:
HANDLE->autoflush( EXPR )
$OUTPUT_AUTOFLUSH
$| If set to nonzero, forces a flush right away and after every
write or print on the currently selected output channel.
Default is 0 (regardless of whether the channel is really
buffered by the system or not; $| tells you only whether you've
asked Perl explicitly to flush after each write). STDOUT will
typically be line buffered if output is to the terminal and
block buffered otherwise. Setting this variable is useful
primarily when you are outputting to a pipe or socket, such as
when you are running a Perl program under rsh and want to see
the output as it's happening. This has no effect on input
buffering. See "getc" in perlfunc for that. See "select" in
perlfunc on how to select the output channel. See also
IO::Handle.
Mnemonic: when you want your pipes to be piping hot
After that, each section is long but very searchable.
But I can see how many people never even noticed."Man page? what's that? what for?"
Expected to know it's there, navigate through it to find the operators or system variables and that you can search through the thing. There are ~260 perl man pages on this computer - not expected to read them. For damn sure expected to use them.
Do read one more section from top to bottom now and then - if the thing is the one fundamental tool in your job!
It was not for not reading the full manual. It was for not using the manual. Somewhere between "not at all", "not competently", "not persistently". And he was pointed to a perl-specific tool which is made for searching the doc. Not the same thing?
And he/they had missed an entire category of symbols. That none of the responses pointed at - their bad on that. That is, all these symbols are described in the same manual section. And used in illustrative examples all over the place. They are not exactly a deep hidden thing.
Also, regarding "flamed". No. Not really. They were handed the same response that countless other questions were getting. Anyone frequenting these forums saw them countless times. It is quite possible that it was their first time on that forum / chat and then that the answer was shocking and traumatic. Yes to that. So that in hindsight, the standard response should have included a pointer to a "how to use the doc" doc. That would have helped. Since it was a generation was seemed unaware of the man pages.
Of course, you aren't under any obligation to spend time helping people who you don't want to, but if a community as a whole reacts this way when someone asks a question, they're making the bet that the there are enough people who are similar enough to them to sustain things in the future. Given that this both happened years ago to the parent commenter and now again when they tell the story again, it's not really that hard to believe that this might have been common enough that a lot of people experienced it. The entire point of this thread is discussing why Perl has faltered, and your explanation in the last paragraph comes across as basically saying "kids these days..." in slightly different words. I'd argue that even if the kids loved man pages, having a condescending attitude towards them would probably still come through in other ways, and that would have had pretty much the same effect.
I agree with you that this probably was a contributor in some people giving up perl quickly. For python or php.
Like I mentioned elsewhere, for people for whom using a book would be a barrier - perl would have been a poor choice anyway. You can't program in perl without using the man pages and books. It's a large language, with lots of features purposely made less visible to the newcomer.
In addition, many people were exposed to perl from web scripts. And it was sooo tempting to just paste in a perl script, and then want to modify it, without spending any time on learning the language. Perl makes that frustrating (and compensates with a stellar course book). I still defend perl by arguing that (in perl) there is no point in discussing what $| might mean even before having covered the basics, for example sigils. The course book is layered, and for good reason: to let you write a program in useful order, fundamentals first. The special variables come up fairly early but then again the course book had an extensive index which includes these special variables first in a symbol section, and then again in the alphabetical order for their wordy version $| or $OUTPUT_AUTOFLUSH. I'm not trying to beat you over the head with the manual. Just pointing out that the course book was throrough and intelligently written.
I'll point out that throwing a question at a forum without poking around it a little to figure out the local mores - well, still now, that will get you barked at. Lesson: Forums would do well to provide a more useful paste-in than "RTFM" - ready to go for their users. Instead of "RTFM". At least if they want to foster adoption. Does any forum do that particiularly well, that you have noticed? Most discords for example, do NOT do that well: it's possible to create stickies and they are really not visible. So people create onboarding documents which then get too long and get skipped. A problem not solved there.