Call A Procedure From Another Package?

in a certain procedure I'm trying to call a procedure from another package in the same Schema. Package-name: Haku_Hops, procedure-name: veto and submitted is a parameter called opnum. So the following brings no problem:

Hops_Haku.veto(opnum);

But what if in the beginning of the package body I create the following variable: hak_pah := 'Hops_Haku.'; Is it then in anyway possible to call this other procedure through this variable, like e.g. hak_pah||veto(opnum);?

Until now I've only gotten error, even after declaring the variable in the declaration part.