a) Why don't you use yum ?
b) run the rpm command with both packages on the command line
Code:
rpm -ivh perl-rrdtool-1.4.4-1.el5.rf.i386.rpm rrdtool-1.4.4-1.el5.wrl.i386.rpm
As you can see
here, the library you need is provided by rrdtool
And all this despite you saying "pls help me !"