plugins/plenv: use _command_exists

plugins/available/plenv.plugin.bash

@@ -1,18 +1,16 @@
+# shellcheck shell=bash
+#
 # plugin for plenv
 
 cite about-plugin
 about-plugin 'plenv plugin for Perl'
 
-if [[ -e "${HOME}/.plenv/bin" ]] ; then
-
-  # load plenv bin dir into path if it exists
-  pathmunge "${HOME}/.plenv/bin"
-
+if [[ -d "${HOME}/.plenv/bin" ]]; then
+	# load plenv bin dir into path if it exists
+	pathmunge "${HOME}/.plenv/bin"
 fi
 
-if [[ `which plenv` ]] ; then
-
-  # init plenv
-  eval "$(plenv init - bash)"
-
+if _command_exists plenv; then
+	# init plenv
+	eval "$(plenv init - bash)"
 fi