philgoetz has asked for the wisdom of the Perl Monks concerning the following question:

NOTE: I'm no longer looking for an answer to this specific question, because I'm using plenv instead. However, I would still like to know whether (and why) CPAN checks the versions of modules installed on @INC, when it should just be managing its own directory of modules.

Many modules fail when I try to install them in CPAN, including CPAN itself. This may be because my CPAN thinks it has lower versions of many modules. For example, 

cpan[12]> upgrade JSON::PP

Package namespace         installed    latest  in CPAN file
JSON::PP                    2.24000   2.27300  MAKAMAKA/JSON-PP-2.2730
+0.tar.gz
Running install for module 'JSON::PP'
Running make for M/MA/MAKAMAKA/JSON-PP-2.27300.tar.gz
  Has already been unwrapped into directory /home/me/.cpan/build/JSON-
+PP-2.27300-dwlFCV
  Has already been made
Running make test
  Has already been tested successfully
Running make install
  Already done

cpan[13]> r JSON::PP

Package namespace         installed    latest  in CPAN file
JSON::PP                    2.24000   2.27300  MAKAMAKA/JSON-PP-2.2730
+0.tar.gz

cpan[14]> quit
Lockfile removed.
]$ rm -rf ~/.cpan/build/JSON-PP-2.27300-dwlFCV
]$ rm -rf ~/perl5/lib/perl5/JSON
]$ rm -rf ~/.cpan/sources/authors/id/M/MA/MAKAMAKA
]$ cpan

cpan[1]> r JSON::PP
CPAN: Storable loaded ok (v2.20)
Going to read '/home/me/.cpan/Metadata'
  Database was generated on Fri, 29 May 2015 14:17:02 GMT

Package namespace         installed    latest  in CPAN file
JSON::PP                    2.24000   2.27300  MAKAMAKA/JSON-PP-2.2730
+0.tar.gz

cpan[2]> force install JSON::PP

...

Result: PASS
  MAKAMAKA/JSON-PP-2.27300.tar.gz
  /usr/bin/make test -- OK
Running make install
Prepending /home/me/.cpan/build/JSON-PP-2.27300-ZHQLK0/blib/arch /home
+/me/.cpan/build/JSON-PP-2.27300-ZHQLK0/blib/lib to PERL5LIB for 'inst
+all'
Manifying blib/man1/json_pp.1
Appending installation info to /home/me/perl5/lib/perl5/x86_64-linux-t
+hread-multi/perllocal.pod
Installing /home/me/perl5/lib/perl5/JSON/PP.pm
Installing /home/me/perl5/lib/perl5/JSON/PP/Boolean.pm
  MAKAMAKA/JSON-PP-2.27300.tar.gz
  /usr/bin/make install -j17 -- OK

cpan[2]> r JSON::PP

Package namespace         installed    latest  in CPAN file
JSON::PP                    2.24000   2.27300  MAKAMAKA/JSON-PP-2.2730
+0.tar.gz

[download]
Why does it keep reporting version 2.24, even after I've removed the module and after I've installed 2.273 again?

Replies are listed 'Best First'.
Re: CPAN frequently reports older module version
by hippo (Archbishop) on May 29, 2015 at 15:27 UTC

    Perhaps that is because it has been installed in some other directory in @INC? Perhaps via a package manager? What happens if you try to locate JSON/PP.pm?

[reply]
[d/l]
[select]
      There are many copies of JSON/PP.pm on the system, but my PERL5LIB is unset, so I think nothing is on @INC. I would think CPAN would not look at @INC anyway. Shouldn't it use only its local install directory? Surely allowing the same CPAN to be used with different library paths would lead to disaster!
[reply]
        my PERL5LIB is unset, so I think nothing is on @INC

        Just dump @INC, so you don't have to guess:

        perl -E 'say for @INC'

        You don't use more than one perl version, do you?

        Alexander

        --
        Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)
[reply]
[d/l]
        There are many copies of JSON/PP.pm on the system

        Is one of them version 2.24 by any chance?

[reply]
Re: CPAN frequently reports older module version
by jeffa (Bishop) on May 29, 2015 at 22:52 UTC

    This is why i use perlbrew on every system i develop on now. Not only does it allow you to control what versionS of Perl you want to work with, it also provides a ready-to-use cpanm client which is a vast improvement over the old interactive CPAN client. cpanm does a pretty good job of removing CPAN modules too.

    jeffa

    L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)
[reply]
[d/l]
Re: CPAN frequently reports older module version
by FreeBeerReekingMonk (Deacon) on May 29, 2015 at 21:17 UTC

    Try to also upgrade your cpan. Type cpan, then inside it type "install CPAN". maybe you do need a higher cpan version... it also rechecks unmet dependencies and has fixed some weird cpan problems for me in the past...

[reply]
      "Many modules fail when I try to install them in CPAN, including CPAN itself."
[reply]

        If your repository is in ~/.cpan then why not move the directory to ~/.cpan.old and try to download again?

[reply]

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