TeX Live on Unix-like systems creates symbolic links from the bin/architecture directory to the relevant script, but the symbolic file links always omit the file extensions. For example, bin/x86_64-linux/latexindent links to ../../texmf-dist/scripts/latexindent/latexindent.pl
This is more consistent with Unix file naming schemes, but the scripts are often distributed with an extension for the benefit of non-Unix-like systems, such as Windows. Since the script is distributed and is on CTAN with the extension, the manual often references the script name with the extension. (If the package/script author isn't aware of this behaviour then they won't think to mention it in the manual.)
Conversely, TeX distributions on Windows may convert the script into an executable, in which case the extension becomes .exe (such as latexindent.exe).
As @cmhughes commented below section 3 of the latexindent manual states:
In what follows, we will always refer to latexindent.pl, but depending
on your operating system and preference, you might substitute
latexindent.exe or simply latexindent.
tlmgr? Did you try updating the repository?sudo tlmgr option repository ctan; sudo tlmgr update --self; sudo tlmgr install latexindent– Andreas Storvik Strauman May 12 '18 at 18:35(running on Debian, switching to user mode!) tlmgr: Remote repository is newer than local (2017 < 2018) Cross release updates are only supported with update-tlmgr-latest(.sh/.exe) --update Please see https://tug.org/texlive/upgrade.html for details.– useranonis May 12 '18 at 18:45sudo tlmgr remove latexindent. Orsudo tlmgr install --reinstall latexmk, but I still think you should upgrade your texlive installation :) – Andreas Storvik Strauman May 12 '18 at 18:53.plextension so it's called as justlatexindentnotlatexindent.pl. – Nicola Talbot May 12 '18 at 19:02tlmgr: Remote repository is newer than local (2017 < 2018)" begs to differ and that TeXLive2018 is not installed, but 2017. You can checktlmgr --versionto make sure. – Andreas Storvik Strauman May 12 '18 at 19:12root\usr\local\texlive\2018. – useranonis May 12 '18 at 19:19.pl; how irritating... – useranonis May 12 '18 at 19:20latexindent.plif you download it. Also if you dols -l \which latexindent`` you will see that it's actually calling the.plfile!In regards to the version, what does
– Andreas Storvik Strauman May 12 '18 at 19:22echo $PATHgive you?