[zsh] Make CTRL-R work with older Perls (#2003)

s///r is only available since perl 5.14. The Perl oneliner
was changed to work with older Perls, possibly even with 5.000.

Fix #2001

shell/key-bindings.zsh

@@ -100,7 +100,7 @@ bindkey '\ec' fzf-cd-widget
 fzf-history-widget() {
   local selected num
   setopt localoptions noglobsubst noposixbuiltins pipefail no_aliases 2> /dev/null
-  selected=( $(fc -rl 1 | perl -ne 'print if !$seen{($_ =~ s/^\s*[0-9]+\s+//r)}++' |
+  selected=( $(fc -rl 1 | perl -ne 'print if !$seen{(/^\s*[0-9]+\s+(.*)/, $1)}++' |
     FZF_DEFAULT_OPTS="--height ${FZF_TMUX_HEIGHT:-40%} $FZF_DEFAULT_OPTS -n2..,.. --tiebreak=index --bind=ctrl-r:toggle-sort $FZF_CTRL_R_OPTS --query=${(qqq)LBUFFER} +m" $(__fzfcmd)) )
   local ret=$?
   if [ -n "$selected" ]; then