As requested by mika, mrud and kafux.
I'm binding the widget to "M-C-h" and "M-C-?" because those are common
codes send by the backspace key in various terminals (and sometimes
terminfo lies about it).
#k# Kill everything in a word up to its last \kbd{/}
bindkey '\ev' slash-backward-kill-word
+#k# Kill everything in a word up to its last \kbd{/}
+bindkey '\e^h' slash-backward-kill-word
+#k# Kill everything in a word up to its last \kbd{/}
+bindkey '\e^?' slash-backward-kill-word
# use the new *-pattern-* widgets for incremental history search
if is439 ; then