I had the same problem and used this snipped in my Emacs' config (you'll need to fine-tune the colours to meet your taste, though):

(eval-after-load 'cperl-mode
  '(progn

;;-- @LanX - not related to your question, but perhaps useful?
;;     (define-key cperl-mode-map (kbd "RET")   'reindent-then-newline
+-and-indent)
;;     (define-key cperl-mode-map (kbd "C-M-h") 'backward-kill-word)
;;     (define-key 'help-command "P" 'cperl-perldoc-at-point)


     ;; experiment: ;; (setq cperl-dark-background "gray14")

     (set-face-attribute 'cperl-array-face nil
                         :foreground  "#ffff88"              ;; "yello
+w3"  "#ffff88"
                         :background  'unspecified
                         :weight      'normal
                         :slant       'normal
                         )
     (set-face-attribute 'cperl-hash-face nil
                         :foreground  "#e08020"              ;; "DarkO
+range3"  "#e080202
                         :background  'unspecified
                         :weight      'normal
                         :slant       'normal
                         )
     ))
[download]

The snipped above is an excerpt from my $HOME/.emacs.d/config/210-setup-cperl.el file that is part of my private Emacs configuration git repository.

It is based on the fine stuff, I've found here: https://github.com/targzeta/emacs-modular-configuration and here: http://whattheemacsd.com

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
[download]

(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... ;-)

Cheers Rolf
_{(addicted to the Perl Programming Language and ☆☆☆☆ :)
Je suis Charlie!}

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)))))
[download]

Faces (emacs lingo for styles) can inherit from other faces.

Albeit I might need to patch cperl-mode cause it already has logic to adapt to background color and terminals.