Paul Evans

Perl, Electronics, General geekery.

Pronouns: he/him
Github: https://github.com/leonerd

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Last Notes

2026-07-06 10:32:35 UTC

I always used to be disappointed when I saw typos or spelling mistakes in online articles, but now I realise I have a small smile of "Ah, at least this shows it was actually written by a human" and often don't worry about them.
What times we live in...

2026-05-05 20:27:47 UTC

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Mouser let me add it to the basket and even pay at the checkout. They then cancelled it before shipping.

2026-05-05 20:17:47 UTC

Today I learned that ADI aren't selling to individuals any more and have instructed all their distributors not to either.. :( So... this kinda sucks. There's now a whole lot of parts for my boards I can no longer buy.
I wonder what the workarounds for this are now..
#electronics

2026-05-01 15:43:36 UTC

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Woo. You achieved a successful migration then.
Looks like I shall try out some of my own today.

2026-05-01 15:41:39 UTC

Do you need to write four bytes of arbitrary content into the page cache of a file you don't own?
You can achieve it with this One Easy Trick. Sysadmins hate it.

2026-05-01 11:31:54 UTC

I don't know why it's called "one-time pad" authentication. I must have used it ten times today at least...

2026-04-30 11:25:40 UTC

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I shall be eagerly watching your (and others') migrations. I may move my own store over that way myself.

2026-04-29 09:28:00 UTC

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Real Names Considered Harmful

2026-04-27 17:18:04 UTC

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I recall getting into a mailing list argument argument about supporting it properly in the in-kernel terminal emulator. It forgot UTF-8ness after a hard reset sequence and had to be configured again using (if I recall correctly) an `ioctl` to set it back again. I felt a detail like that should be remembered.

2026-04-26 16:55:10 UTC

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Whenever I get a low memory warning, I take a look around the web at RAM modules for sale. Then the prices scare me so much I close the entire browser process.
Which admittedly does solve the problem ;)

2026-04-25 07:34:34 UTC

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Thanks for your (personal) efforts in trying to keep us informed. Though, I fear your company's reputation will take quite a dent for this incident.

2026-04-23 06:54:30 UTC

First morning of Perl Toolchain Summit is going well. What I thought was the coffee button on the machine at breakfast turned out to be hot chocolate. So now instead of waking me up after my nearly-midnight arrival, I'll be even more asleep before we start. #pts2026

2026-04-23 06:51:30 UTC

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I can't help with your question, but I do find it amusing that urban birds are picking up man-made noises. Near me a lot of them have learned to imitate the alarm noises on Lime bikes

2026-04-19 19:04:00 UTC

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I've been with them continuously for the past nearly 20 years. Thoroughly decent folks full of clue and competence. Would recommend

2026-04-18 10:10:31 UTC

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That's printed by Test::More directly to STDOUT. It's not part of TAP, or performed by `prove`

2026-04-17 14:16:55 UTC

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Yes the total silence from them is the most annoying thing jere.
Tindie: Please tell us what's going on, and whether we can expect things to ever come back, at this point. Otherwise we may start to assume the worst.

2026-04-09 20:05:12 UTC

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Yup, we take the whole back-compat thing seriously. If you want to write a script that'll still work in a decade or two, write it in Perl.

2026-03-28 12:04:02 UTC

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Amused that there is both a "TRY NOT" and a struck through "TRY"

2026-03-28 00:04:51 UTC

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Clouded leopard. One of these guys
https://www.nationalgeographic.com/animals/mammals/facts/clouded-leopard
Ones you see at zoos and animal rescue places are very friendly with their keepers, so I imagine I'd have no trouble with it. Plus it's a cat. Cats are always cool.

2026-03-27 17:32:39 UTC

A new blog post on the nature of #CPAN-based experiments at adding new syntax and features to the #Perl language.
Or at least, the first half before I get around to writing the thing I was actually going to say, in likely a follow-up post next week.
https://leonerds-code.blogspot.com/2026/03/cpan-based-experiments-reminder.html

2026-03-26 17:17:30 UTC

Hah, today I just did
"Wouldn't it be great if {an option for this tool to solve my problem} exists?"
read manpage
"Oh, hah. That actually exists, with the name I actually suggested. Good good."

2026-03-26 00:21:52 UTC

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Indeed so, in fact it was quite a bug waiting to happen. Before that change, I was about to make a bugfix and then realised I would have to edit both sides of the ifdef, and then arrange to test both sides as well. It seemed not worth the trouble just for those two old versions (5.18, 5.20).

2026-03-25 13:55:22 UTC

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It always annoys me that ASCII and thereafter Unicode always said they weren't going to add formatting mechanisms, as that was for other people. And so instead Markdown invented a way to be always ambiguously unsure about the meanings of regular ASCII punctuation to stand in for formatting requests.
Just think what we could have had instead...

2026-03-24 12:57:13 UTC

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Ahhh; much tidy
```
13 files changed, 15 insertions(+), 261 deletions(-)
```

2026-03-24 12:38:26 UTC

Today I have decided to bump the minimum #Perl version requirement of Object::Pad up from 5.18 (released in summer of 2013), to 5.22 (released in summer of 2015). This has allowed me to remove quite a lot of ifdef-guarded code, as well as plenty of workarounds for missing things (the UNOP_AUX and PADNAME types) in those older perl versions.
This sort of spring cleaning is useful to do every once in a while.

2026-03-20 18:15:16 UTC

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I usually sideload bread into my toaster. I buy bread from a different company than that which made my toaster.
(Well, I load the bread in from the top like a normal toaster. ;) )

2026-03-16 14:49:45 UTC

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Debian, XFCE, Sawfish.

2026-03-16 13:51:46 UTC

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Yeah that got it.

2026-03-16 13:51:34 UTC

Ahhh - there it is, lovely :) I was looking in the "Interface" section, as I imagined that's where it would be.

2026-03-16 13:43:36 UTC

Actually for that matter, does anyone know how to actually move the #Steam window on the screen in #Linux ?
You'd think you just drag it from the top bar and indeed it moves, but it does something super weird to the mouse so the very next time you click the mouse the window jumps back to its original location.

2026-03-16 13:39:19 UTC

Does anyone know how to set the font size on the #Linux #Steam client? It's tiiiiiiny. I can't read it on my laptop screen. I usually set everything a lot bigger than this.

2026-03-15 12:06:49 UTC

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Yes I'm feeling nervous just looking at it. That said I don't think the terrible perspective on the photo composition job is helping matters

2026-03-15 10:10:14 UTC

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Sometimes I declare a bug to be a bath-worthy problem. Once I run the bath I'm kinda committed to lazing in it for an hour and just thinking

2026-03-10 14:17:32 UTC

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When you say "per person", is that per person in the donating country, or the receiving one?

2026-03-05 10:56:58 UTC

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Who is the "us" in this headline?

2026-03-02 14:38:48 UTC

Do you know what I think?
Donald Trump's bored of peace

2026-02-28 00:03:45 UTC

Uhhhh... None of the above?
https://cdn.fosstodon.org/media_attachments/files/116/145/322/295/693/227/original/8f45a7b1bf247b0d.png

2026-02-24 22:50:18 UTC

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Yeah, I didn't really want a higher resolution. All it means is I turn up the font sizes on everything and get the same amount of text on the screen but now it has slightly smoother curves to it. Overall it doesn't really feel worth it.

2026-02-24 21:45:49 UTC

Does anyone know how I can set the default zoom for all of Google Docs/Sheets/etc... to some number bigger than 100%?
Since I bought a laptop in the past, ohhh... five years, I have a screen resolution sufficiently high that the default font size is tiiiiiiiny.

2026-02-24 16:41:09 UTC

I think my todo list only grows over time. It's a good thing I don't have any children or they'd have to inherit it, and I wouldn't wish that on anyone

2026-02-21 16:30:36 UTC

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Then assist with writing it?

2026-02-12 16:49:05 UTC

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I've occasionally pondered a `returnif` keyword. Basically `my $tmp = EXPR; return $tmp if $tmp;` but without the temporary

2026-02-11 14:44:10 UTC

A comment I just posted on /r/perl defending my decision to increase the minimum supported #perl version to 5.20 on a lot of my #CPAN modules.
https://www.reddit.com/r/perl/comments/1qwzhc6/comment/o4t0p4a/

2026-02-11 09:10:23 UTC

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Did Windows 95 actually come with a Hotdog Stand theme? I only remember it from 3.1

2026-02-08 14:48:33 UTC

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Ooh, cute ;) Though in my case one of the devices is a Raspberry Pi, so it wouldn't work here.

2026-02-08 14:34:42 UTC

They say you can't directly link two computers by a USB cable. But I don't believe those people.
https://cdn.fosstodon.org/media_attachments/files/116/035/499/870/824/575/original/01d3746cb953a545.jpg

2026-02-07 21:48:11 UTC

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Mmm; cute idea though I don't like the `setcap` approach for this particular problem, because the binary would be /usr/bin/perl and that feels a bit of a heavy shotgun to apply in this case.

2026-02-07 21:42:49 UTC

Looking for software recommendations, for a Raspberry Pi.
Smallest/lightest way to redirect TCP port 80 over to some high-numbered port for running an http server as non-root.
I *could* run lighttpd or haproxy or somesuch; but is there anything even smaller?

2026-02-07 14:14:19 UTC

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I don't know as if the history is saved anywhere. Probably your best bet is to hunt all the `.packlist` files in $PERL5LIB and sort by modtime

2026-02-06 22:18:49 UTC

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Have you considered 3-space? ;)

2026-02-06 16:08:49 UTC

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Yeah; unfortunately the language design is too deeply ingrained that control-flow statements and value expressions are two different things. See also if/else vs ? :, foreach vs map, etc etc.
Scheme by comparison has no such distinction; it'd be a nicer way to work.

2026-02-05 17:01:32 UTC

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Ahhhhhh!

2026-02-05 10:14:30 UTC

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:1,$d works just as well in vim or nvim
If you did want to do that visually there's ggdG

2026-02-05 00:01:46 UTC

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Version numbers in particular

2026-02-03 12:46:43 UTC

Some people have a TODO list. Or a TODO heap. For me I think it's more of a TODO directed graph.
At this point I'm not even sure it's acyclic.

2026-01-28 23:18:00 UTC

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What do you mean, you no longer need a dedicated logging facility constant for UUCP?

2026-01-28 09:40:23 UTC

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Kinda like those model villages that depict the place where they are, so they include a tiny model of themselves.
This one being one of my favourites: The model has two further recursive copies as models, and a final one in just paint.
https://en.wikipedia.org/wiki/Bourton-on-the-Water_model_village

2026-01-19 13:47:42 UTC

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For context, assuming a global population of 9 billion people, that's $277 for every single person on Earth.

2026-01-19 11:17:02 UTC

This has real @npub1g8x…7wul energy
A TV remote control using floppy disks
https://hackaday.social/@hackaday/115920966006526350

2026-01-17 13:52:08 UTC

I made a thing. I now need to post it from UK to Europe. How on earth do people do that these days? I have to work out a 4 (6?) digit HS customs code for it. How do I know it's even approximately correct?

2026-01-16 17:01:34 UTC

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Fairly sure that Salvador Dali painted one of these

2026-01-15 17:33:46 UTC

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Wow, that's going to be very dated indeed. We've added a lot of good stuff in the past 26 years ;)
https://sheet.shiar.nl/perl

2026-01-15 00:29:14 UTC

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What happens if you try to put in a date in the future?

2026-01-13 15:51:38 UTC

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"Did you mean: stop time?"

2026-01-13 15:15:41 UTC

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In absolute terms it's tiny because this program does very little CPU work - it's just a monitoring bridge between a serial port and an HTTP prometheus "metrics" exporter.
But still - a drop from 0.24% with the pureperl to 0.20% with XS, means the XS module does speed the program up by about 20%.
It's nice to be able to so easily see on a graph such a performance improvement by using the XS version, which might otherwise be somewhat hard to measure.

2026-01-13 15:13:50 UTC

During my recent debugging of a `Future`-related memory leak issue, I had occasion to swap a program from using `Future::XS`, to the pure-perl `Future::PP` implementation instead.
As the program runs a very flat stable CPU load, such a change made it easy to see the performance different such a change made.
https://cdn.fosstodon.org/media_attachments/files/115/888/424/210/759/028/original/61c8d9298bb52895.png

2026-01-13 14:52:50 UTC

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And here it is.
https://metacpan.org/release/PEVANS/Future-XS-0.15
That concludes this particular story, though I have at least two follow-up thoughts to add, but I'll write those in separate threads. I think this one has gone on long enough now.

2026-01-13 12:59:58 UTC

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Success :) Having left this version of the code running for over 24 hours, it indeed hasn't shown any signs of a leak.
I think we're onto a winner here, I'll pop this up on CPAN.
https://cdn.fosstodon.org/media_attachments/files/115/887/904/018/864/066/original/4fd591a3633dab3a.png
https://cdn.fosstodon.org/media_attachments/files/115/887/904/021/647/443/original/1b4a1f411d60576b.png

2026-01-12 15:38:33 UTC

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Another in the same vein:
https://fosstodon.org/@leonerd/115649681945671656
#note1xcm…exgd

2026-01-12 12:56:27 UTC

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With this one-line fix in place, the newly-added unit test passes at least.
I'll put this code on my real machine and see how it holds up. If that appears to fix it, then I'll ship it to CPAN as the next version of `Future::XS` tomorrow.
https://cdn.fosstodon.org/media_attachments/files/115/882/233/826/053/574/original/10193ec28b7e39d8.png

2026-01-12 12:53:58 UTC

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Knowing the shape of the code around handling of `Future::Exception` instances, it didn't take me too long to poke around and find a place where a reference is accidentally retained.
After a nested call to the `Future::Exception->new`, the result if `SvREFCNT_inc()`ed to retain it over the `FREETMPS; LEAVE;` at the end of the method call, but we forgot to re-mortalize it when pushing it to the stack for the next call.
An additional `sv_2mortal()` is needed.
https://cdn.fosstodon.org/media_attachments/files/115/882/224/687/270/218/original/683828774512498a.png

2026-01-12 11:53:34 UTC

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For an extra bit of confirmation that this seems to be the bug we're looking for, we can also inspect the `.pmat` files that the failing test wrote.
By running both through the `pmat-diff` tool, it compares the gained and lost SVs on each side, and tries to associate them together. It'll draw a summary of what it finds:
Here we indeed find an ARRAY blessed as `Future::Exception`, holding five other SVs. Seems to match what we'd expect.
https://cdn.fosstodon.org/media_attachments/files/115/881/976/402/838/110/original/e205636fa8b25dd6.png

2026-01-12 11:45:45 UTC

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Knowing the source of the leak is in `Future::XS` helps narrow it down. That's not a big distribution, not many lines of code that deal with `Future::Exception` objects anyway.
It didn't take me long to manage to write a test using `Test::MemoryGrowth` that indicates failure:
https://metacpan.org/pod/Test::MemoryGrowth
https://cdn.fosstodon.org/media_attachments/files/115/881/948/359/969/951/original/895472f04c122841.png
https://cdn.fosstodon.org/media_attachments/files/115/881/948/365/451/177/original/61ce683f99cab927.png

2026-01-12 11:39:23 UTC

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I left this running without `Future::XS` over the weekend to see what would happen.
It did use a constant amount more memory than with (that's to be expected), but it didn't grow at all over the time. Moreover, the per-class breakdown doesn't show any growing collection of `Future::Exception` objects at all. It seems we are on the right path.
https://cdn.fosstodon.org/media_attachments/files/115/881/924/933/326/600/original/4b94c4b20c4eb736.png

2026-01-09 14:34:16 UTC

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Quite so. As I said, I suspect a missing `SvREFCNT_dec()` call somewhere in one of my XS modules. The trick now is identifying which module and where it should go.
Missing code is always the hardest kind to find. ;)

2026-01-09 14:25:26 UTC

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Well the failure itself comes from this line here:
https://metacpan.org/dist/Device-Serial-SLuRM/source/lib/Device/Serial/SLuRM.pm#L707
but knowing this isn't directly any help. The problem is that something somewhere is retaining these exception objects indefinitely and not throwing them away. That's the part I need to investigate.

2026-01-09 14:21:33 UTC

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It also turns out that I forgot to actually document the way to skip loading the `Future::XS` module, so I can't link to any docs of that for this thread ;)
While I leave this to run overnight again and maybe or maybe-not accumulate any more leaks, I can spend a moment to write about that ;)
I think that's enough for today, I'll wait and see what this yields tomorrow...

2026-01-09 14:19:47 UTC

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At this point there are no more immediate steps we can take, so we will have to try a few other ideas.
Knowing the surrounding code, I know there's a couple of XS-implemented modules around Future handling, so it seems likely one of those has forgotten to `SvREFCNT_dec()` an exception reference.
One of those modules, `Future::XS`, is an optional performance improvement and can be skipped. By restarting the program without it we can wait and see if the problem continues.

2026-01-09 14:11:58 UTC

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Next we can try using the `identify` command on this example object, to see what is retaining it, and hopefully gain some insight into the actual bug.
Unfortunately for us, this doesn't lead anywhere. The ARRAY is being held by a scalar REF instance, but nothing in the heapdump can find what is holding on to that.
https://cdn.fosstodon.org/media_attachments/files/115/865/540/636/144/918/original/88e1323bcabd2e68.png

2026-01-09 13:45:23 UTC

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Picking one of these at random, we can inspect it to see its contents.
The message says it's about a timeout that happened, which again seems to correlate with the occasional staircase shape. These timeouts were rare, so it seems these exception values have been retained by something somewhere.
https://cdn.fosstodon.org/media_attachments/files/115/865/429/555/710/464/original/125321248d772c48.png

2026-01-09 13:24:17 UTC

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Next, loading the second file into the `pmat` tool shell lets us poke at it in more detail. Since we already have a good ldea it's related to these `Future::Exception` instances, lets start by grabbing a list of those.
Seems like there's quite a few.
https://cdn.fosstodon.org/media_attachments/files/115/865/352/672/740/746/original/82f520bbf960b589.png

2026-01-09 12:36:13 UTC

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First port of call is the `pmat-counts` script, which counts a summary of how many of various types of SV are found in the dump files. When given more than one file in a row, it also prints a count of differences of each file from the previous.
Here we can definitely see the second file has grown in various categories, including adding a bunch of blessed ARRAYs, which seems to agree with the graphs.
https://cdn.fosstodon.org/media_attachments/files/115/865/160/870/985/313/original/7b5dc61c060a0016.png

2026-01-09 12:03:39 UTC

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The reason for that restart in the middle was so I could load `Devel::MAT::Dumper` into the process. This let me take two heapdump files; one shortly after startup, and one much later after an accumulation of these Future::Exception objects.
I did this by using the `-dump_at_SIGQUIT` option, and sending a SIGQUIT to the running program each time.
I now have two `.pmat` files, so I can compare them for differences.
https://metacpan.org/pod/Devel::MAT::Dumper#-dump_at_SIGQUIT

2026-01-09 11:51:06 UTC

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Looking on the more detailed graph, it seems there's one object class in particular of note that seems to correlate to this upwards growth: Future::Exception.
This seems reasonable, as from the staircase shape of the graph, the growth appears to come in occasional bursts, around longer otherwise-stable periods.
https://cdn.fosstodon.org/media_attachments/files/115/864/983/477/469/044/original/aad0b7b3027c8d8b.png

2026-01-09 11:47:58 UTC

It seems my #Perl memory leak issue is ongoing. While I managed to fix one big one, it turns out there's still a *slight* heap growth ongoing:
This time I'm going to post about debugging it in real-time, so this will be more of a story of exploration.
It starts with a monitoring graph, in which I noticed still a slight upwards trend. I restarted the process in the middle here with some extra debug modules loaded.
https://cdn.fosstodon.org/media_attachments/files/115/864/967/971/264/716/original/1be9375f124f4379.png

2026-01-08 14:26:00 UTC

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Yes, I fixed it. Various graphs helped me find what the problem was

2026-01-08 13:19:36 UTC

It used to have a memory leak. Now it doesn't.
Fixed by the help of `Net::Prometheus` and extended #Perl heap monitoring metrics.
https://metacpan.org/pod/Net::Prometheus
https://cdn.fosstodon.org/media_attachments/files/115/859/668/688/073/156/original/52521cc8c16a9e06.png

2026-01-07 17:36:44 UTC

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vim
Really, plain nroff with the `man` macros isn't too bad to write by hand

2026-01-06 17:06:52 UTC

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Because why sell something for $10 when you can offer a $2/month subscription and hope that people forget to cancel it after 5 months.

2026-01-05 10:54:31 UTC

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So many updates along similar lines as this. Just little neatening updates that remove some of that annoying argument-handling noise.
https://cdn.fosstodon.org/media_attachments/files/115/842/114/058/249/130/original/4dc2af9f83727196.png

2026-01-04 23:54:35 UTC

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Depends on your server, and even then you have to specifically enable it

2026-01-03 15:58:58 UTC

I have decided that any new releases of existing #CPAN modules that I make will now be bumped up to needing at least perl 5.20 (except in a few odd cases).
This means they can now all use a bunch more new features such as signatures. The benefits purely on line-count, readability, and the basic argument checking that it gives, already seem worth it.
Already any new dists I make tend to be 5.36+ or 5.38+ if using `class`; but this now applies to existing ones as well
#perl

2026-01-01 20:55:25 UTC

Last night, my indoor PM10 sensor managed to quite easily detect all the smoke from the local fireworks going off all around me.
https://cdn.fosstodon.org/media_attachments/files/115/821/823/607/287/691/original/65a683c5938757d9.png

2025-12-30 19:56:09 UTC

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"If" we're interested? C'mon, you know your audience... ;)

2025-12-29 19:50:42 UTC

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Because, in the words of George Mallory, it is there?

2025-12-29 19:48:12 UTC

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I think this is basically a Star Trek staple. Not just Voyager, but often in TNG too people would treat information like a unique asset, something at risk of being lost. As if the idea of just taking copies had been forgotten by the 24th century.
Maybe the all-pervasive DRM was just everywhere by then? :/

2025-12-24 11:51:38 UTC

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My point was more about not committing the current state into long-term paper, because the current state keeps changing. For example, abstract classes aren't a thing yet but I hope to have something in place by next summer's yearly release.

2025-12-24 10:15:18 UTC

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And then more editions as things keep changing?

2025-12-17 08:21:56 UTC

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Probably not too difficult. Perhaps you want to suggest it as a PPC?

2025-12-16 13:59:09 UTC

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We post a summary of every meeting. We don't always meet every single week.