Perl install module Gtk: Can't exec 'gtk-config'

[<kuepperspeter compuserve de>]

Hello,

when I tried to use a program with Perl, I got the error "Can't locate 
Gtk.pm in @INC"
so I started to install the module Gtk (the pakets of gtk und gtk-devel 
with gtk-config were already installed on my system): 
perl -MCPAN -e shell
cpan> install Gtk
...
CPAN.pm: Going to build M/ML/MLEHMANN/Gtk-Perl-0.7009.tar.gz
Can't exec "gtk-config": No such file or directory at Makefile.PL line 
141.
Package 'gtk' needed but it was not detected on your system.
You may want to force it using --with-gtk-force if you know better than 
me.

Then I tried "export GTK_CONFIG=/opt/gnome/bin/gtk-config" but I got 
the same error.

How to tell Perl or cpan to use the correct path to gtk-config?

Thanks for any help.

Peter