Thanks!

But my problem was rather that I wanted to have a generic solution which works with all themes which forgot to define the cperl-hash and array face. (some do)

ATM I'm using M-x customize-face ² to derive array and hash face from the normal variable face.

Customize face (default `all faces'): cperl-array-face

Operate on all settings in this buffer:
 [Revert]...   [Apply]   [Apply and Save] 

Hide Cperl Array Face:[sample]
    State : EDITED, shown value does not take effect until you set or 
+save it.
   Font Lock mode face used to highlight array names.
INS DEL Display: all
               [X] Weight: bold
               [X] Slant:  italic
               [X] Inherit:
                   [INS] [DEL] Face: font-lock-variable-name-face
  
               Show All Attributes
INS
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(Note: Display:All is important)

after hitting "Apply and Save" this will be executed at the end of all my configs.

Seems to work well ATM and I don't need to fiddle with elisp... ;-)

²) or click Options -> Customize Emacs -> Specific Face

update

that's the generated lisp code which "customize" wrote into my init.el

(custom-set-faces
 ;; custom-set-faces was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 '(default ((t (:family "Courier New" :foundry "outline" :slant normal
+ :weight bold :height 113 :width normal))))
 '(cperl-array-face ((t (:inherit font-lock-variable-name-face :slant 
+italic :weight bold))))
 '(cperl-hash-face ((t (:inherit font-lock-variable-name-face :slant i
+talic :weight bold)))))
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