[Solved] Suspected Perl issue on my Debian Sid install

[milomak]

So when I try to run a couple of commands

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apt-file update
cpanm
cpan -u

My perl version

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# perl -v

This is perl 5, version 26, subversion 0 (v5.26.0) built for x86_64-linux-gnu-thread-multi
(with 51 registered patches, see perl -V for more detail)

I get the following error

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# cpan -u
ListUtil.c: loadable library and perl binaries are mismatched (got handshake key 0xdb80080, needed 0xde00080)
#

ListUtil.c doesn't seem to exist

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# locate ListUtil.c
#

from the searching I have done, it seems cpan (or cpanm) is the favoured route to update the libraries. But of course this problem seems to be preventing me from running them.

Now I don't know if this is related, but I noticed all this when an update failed with a debconf error

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# dpkg -i /var/cache/apt/archives/debconf_1.5.63_all.deb
(Reading database ... 290546 files and directories currently installed.)
Preparing to unpack .../debconf_1.5.63_all.deb ...
Unpacking debconf (1.5.63) over (1.5.63) ...
Setting up debconf (1.5.63) ...
ListUtil.c: loadable library and perl binaries are mismatched (got handshake key 0xdb80080, needed 0xde00080)
dpkg: error processing package debconf (--install):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 debconf

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# dpkg-reconfigure debconf
ListUtil.c: loadable library and perl binaries are mismatched (got handshake key 0xdb80080, needed 0xde00080)

Now this may have been my fault by installing it anyway even with a bug listed

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# apt-listbugs list debconf
Retrieving bug reports... Done
Parsing Found/Fixed information... Done
grave bugs of debconf (→ ) <Outstanding>
 b1 - #709198 - debconf: should not use python in maintainer scripts
Summary:
 debconf(1 bug)

But another 2 sid installs I have are running the same version of debconf and they are fine so I am not sure if this is a red herring.

Any thoughts would be appreciated

edit - the one difference the install with an issue has is that I tried to install a musicbrainz server on it

[milomak]

so yes trying to install musicbrainz server was what was causing issues as this installed perl modules via cpanm

lessons learnt:
- i might be a user of 10+ years on sid, but that doesn't mean i should not be prepared for things going north
- given the above it's especially important to remember that most guides will be done with the view of a stable install
- i have to be very careful with perl especially as it introduces packages outside of apt

1. so because i am on sid, perl had upgraded from 5.24 to 5.26
2. downgraded to 5.24 (the version in stable) using dpkg
3. cpanm was then able to work and I removed List::Util - cpanm --uninstall List::Util
4. upgraded perl back to the sid version
5. had to repeat steps 2 to 4 a number of times as new perl modules showed up that were impacted
6. eventually got the system to a point where the debconf install completed and I could do a full system upgrade

edit:
- further to realising that this was related to trying to install musicbrainz,
- I deleted in root .cpan/ and .cpanm/
- and then in root, edited .bashrc to remove eval $( perl -Mlocal::lib )
- this seems to have solved the issue