Can any one tell me what do I need to do?

Step 1) install "Informix" client libraries (apt-get ... sh configure ... whatever your OS preferred method

This is talked about in
https://metacpan.org/source/JOHNL/DBD-Informix-2013.0521/README
https://metacpan.org/source/JOHNL/DBD-Informix-2013.0521/Notes/FAQ

Step 2) reinstall DBD::Informix (either apt-get ... or  cpan DBD::Informix )

Thats about it