Free perquisite

Unlike other perquisite, which will not improve the skills of the employee (but only keeps him happier), it is not a perquisite because the certified program is enhancing the skills of employee, and is similar to training (though not an actual training), because of which it is benefiting the company by better performance of the employee. 

Also, in other perks, just by keeping the employee happy, he might perform efficiently and with more efforts, but doent really mean his skills will improve out of nowhere. No doubt he could be working harder. :)