Solved:

"I feel, that somehow, I need to tell cpan, that I have a v5.22.1 perl version and not 5.20.2, so it installs module in the correct folder. How can I do it? Or how can I fix this?"

If you have multiple version of perl installed, each perl will have a version of cpan.

marto@laptop:~$ which cpan
/usr/bin/cpan
[download]

Simply calling cpan Module::Name will invoke the first cpan in your PATH environment variable. Either provide the full path to cpan for the version of perl you want to install modules to (/app/perl26/bin/cpan Module::Name) or alter your PATH, giving precedence to the directory containing your target Perl installation. Also, consider using cpanm over cpan, it's faster.

No, I don't have mutiple versions of perl. It's just updates automatically from ubuntu's repository.
which cpan just shows:
/usr/bin/cpan

If as you say perl -v reports v5.22.1 but cpan is installing to /usr/local/lib/x86_64-linux-gnu/perl/5.20.2/ it looks as though a Ubuntu has done something weird, which wouldn't be unheard of, for example. Do you have a #!/usr/local/bin/perl if so which version? Did you try using cpanm?

My preference, for an easy life, is to install my own version of perl elsewhere, and leave the system one alone. A custom install has resulted in fewer headaches. See also perlbrew.

Forgive my skepticism. You can confirm or refute this easily enough with locate -r /bin/perl$.

You could also say which version of ubuntu you have installed so we can determine which perl is the interloper.

I've installed Tk with cpan

Why? there's a prebuilt perl-tk package in the ubuntu repository. As for Ubuntu 16.04.3 LTS:

qwurx [shmem] ~> dpkg -l perl-tk
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/T
+rig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name              Version       Architecture  Description
+++-=================-=============-=============-====================
+====================
ii  perl-tk           1:804.033-1bu amd64         Perl module providin
+g the Tk graphics li
[download]

Since you are using the system perl, you should use the packages provided by your systems package manager

user@system:~$ sudo apt-get install perl-tk
[download]

and install via cpan/cpanm only if you absolutely need a different version.

Fixing your cpan would be the answer as above, but you can use the following to add an extra directory (or more) for your script to access modules not in your usual path: http://perldoc.perl.org/lib.htm

"Fixing your cpan would be the answer as above, but you can use the following to add an extra directory (or more) for your script to access modules not in your usual path: http://perldoc.perl.org/lib.htm"

cpan isn't broken, and doesn't require fixing. Note that your suggestion introduces the binary incompatibility problem.

As a side note What shortcuts can I use for linking to other information?, [doc://lib] -> lib.

the http://perldoc.perl.org/lib.htm url resolves to 404

Should be, .html, perlmonks takes care of all this for you via [doc://lib] -> lib.

the http://perldoc.perl.org/lib.htm url resolves to 404

it works for me, maybe you need to try again?

Cheers, Sören

Créateur des bugs mobiles - let loose once, run everywhere.
(hooked on the Perl Programming language)