In most cases you need an ODBC driver manager installed before installing DBD::ODBC (a very few ODBC drivers work with it directly but that is no longer recommended).

DBD::ODBC is mostly C code and XS and you need the driver manager C header files in addition to the driver manager itself. That probably means (in these days of packages) you need unixodbc main package and unixodbc-dev package.

Looking for odbc_config on PATH
  odbc_config not found        
Looking for iodbc-config on PATH
  iodbc_config not found        
odbc_config not found - ok, there are other things I can do
[download]

More modern versions of unixODBC and iODBC contain a config program ((x)odbc_config) which makes DBD::ODBC's life of configuring and itself to match the many different ways driver managers can be built a lot easier. As a result, DBD::ODBC looks for Xodbc_config first. In you case your installed odbc driver manager is too old for that so it is falling back on trying to locate driver manager header files:

Still trying to guess ODBCHOME - looking for headers now   
  trying /usr/include                                      
  trying usr/local/include                                 
  trying /usr/pkg/include                                  
  trying /usr/local/easysoft/unixODBC/include
[download]

It looks to me like you have not installed unixodbc-dev package that contains the headers or you installed in a non-standard place and did not use ODBCHOME or -o to point to them.