G'day yysachinyy,

Welcome to the Monastery.

"I tried setting PERL5LIB and use lib pragma ... but din't help." [sic]

You don't show exactly what you did: here's some pointers.

• PERL5LIB needs to be set before you call your scripts and made available to them (e.g. via export).
• use lib should be used before use DateTime; be careful of relative paths.
• Check that @INC has the path you set: consider doing so in a CHECK or INIT block.
• Are you running in "taint mode"? See -T and -t in perlrun. See perlsec and, in particular, the "Taint mode and @INC" section.
• Are you using the warnings pragma?

"I would like to know how Perl gurus/monks solve and contribute to CPAN Module."

My basic process would be as follows. I'll reference the current DateTime module; however, this would be what I'd generally use for any module. You may have different methods for achieving each step — I'm certainly not trying to recommend you use different tools — but the order of steps should be much the same. And, of course, the commands I've used are just examples.

1. Set up a work area.

   $ cd /some/base/work/dir
   $ mkdir DateTime
   $ cd DateTime
   [download]

2. Get the currrent distribution.

   $ wget http://search.cpan.org/CPAN/authors/id/D/DR/DROLSKY/DateTime-1.
   +41.tar.gz
   $ tar zxvf DateTime-1.41.tar.gz > DateTime-1.41.INSTALL 2>&1
   $ view DateTime-1.41.INSTALL  # Check there's no errors
   $ cd DateTime-1.41
   [download]

3. Read any relevant documentation.

   $ view README  # That's "README.md" for this distro
   $ view INSTALL
   [download]

4. Modify the module code.

   $ cd lib
   $ vi DateTime.pm
   [download]

5. Write new test(s).

   $ cd ../t
   $ vi new_test.t
   [download]

6. Create Makefile, build and test.

   $ cd ..
   $ perl Makefile.PL
   $ make
   $ make test
   [download]

7. Repeat the last three steps until the code does what you want and the tests all pass.

   $ make realclean
   $ # ... repeat commands already shown ...
   [download]

See also: "PAUSE: The [Perl programming] Authors Upload Server".