The command align-regexp is written to prompt you for a regular expression if you use it interactively.
The following code does what you describe you want.
(defun my-common-align (begin end)
"Align text in the region on '=' and '<-'."
(interactive "r")
(let ((common-align-regexp "\\(?:=\\|<-\\)"))
(align-regexp begin end common-align-regexp)))
(global-set-key "\C-a" 'my-common-align)
The choice of key is yours, but `C-a' is move-beginning-of-line almost everywhere. I might recommend `C-c a' instead.
,Douglas
Douglas Lewan
Shubert Ticketing
(201) 489-8600 ext 224
If the majority of cooking accidents happen in the kitchen, then why don't we just cook in other rooms?