It's been quite a few years since I set up Cygwin & Perlbrew. I'll provide what information I can: some current and some quite old.

My current Win10 — what I see when I start cmd.exe:

Microsoft Windows [Version 10.0.19045.6159]
(c) Microsoft Corporation. All rights reserved.

C:\Users\ken>
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My current system (Cygwin) information:

$ uname -a
CYGWIN_NT-10.0-19045 titan 3.6.4-1.x86_64 2025-07-15 07:55 UTC x86_64 
+Cygwin
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I originally set up Cygwin using the installer on the Cygwin site; I have updated that many times over the years (currently at 3.6.4).

As far as I remember, I originally set up Perlbrew from the instructions on that page:

For a quick installation, do this:

\curl -L https://install.perlbrew.pl | bash
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It would appear that I did this about six years ago and haven't changed it since:

$ which perlbrew
/home/ken/perl5/perlbrew/bin/perlbrew

$ ls -l /home/ken/perl5/perlbrew/bin/perlbrew
-rwxr-xr-x 1 ken None 1316905 Jul 26  2019 /home/ken/perl5/perlbrew/bi
+n/perlbrew
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I've been installing Perl versions using instructions a little further down on that page. This is what I used yesterday.

To install the latest stable release ...

perlbrew install perl-5.42.0
perlbrew switch perl-5.42.0
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This installed Perl v5.42.0 cleanly on the first run; no test or other errors.

I've also installed other Perl versions, stable & development, over the years:

$ perlbrew list
 * perl-5.42.0
   perl-5.40.0
   perl-5.39.3
   perl-5.38.0
   perl-5.36.0
   perl-5.34.0
   perl-5.33.5
   perl-5.32.0
   perl-5.30.0
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I really can't help with the error information that you've posted. You may want to start (almost) from scratch:

1. Get Cygwin up-to-date. I do this by downloading the Cygwin Installer (setup-x86_64.exe) then running that from Win10: File Explorer.
2. Reinstall perlbrew using the instructions shown above.
3. Reinstall Perl v5.42.0 using the instructions shown above.

I'll also advise you to run the latest setup-x86_64.exe regularly — I generally aim to do this weekly so that it only takes some tens of minutes — otherwise you may find it takes hours if left for an extended period of time.

Good luck!