--- perl-module.eclass	2015-03-15 12:49:17.976368033 +1300
+++ perl-module.eclass	2015-03-15 13:40:12.750005314 +1300
@@ -114,6 +114,8 @@
 	[[ ${SRC_PREP} = yes ]] && return 0
 	SRC_PREP="yes"
 
+	perl_check_env
+
 	perl_set_version
 
 	[[ -z ${pm_echovar} ]] && export PERL_MM_USE_DEFAULT=1
@@ -548,3 +550,44 @@
 		popd > /dev/null
 	fi
 }
+
+# @FUNCTION: perl_check_env
+# @USAGE: perl_check_env
+# @DESCRIPTION:
+# Checks a blacklist of known-suspect ENV values that can be accidentally set by users
+# doing personal perl work, which may accidentally leak into portage and break the
+# system perl installaton.
+# Dies if any of the suspect fields are found, and tells users the circumvention options
+# for the problem, whether it be unsetting the bad fields, or setting 
+# I_KNOW_WHAT_IM_DOING=1
+perl_check_env() {
+	local warned value;
+
+	for i in PERL_MM_OPT PERL5LIB PERL5OPT PERL_MB_OPT PERL_CORE PERLPREFIX; do
+		# Next Loop unless match
+		[ -v $i ] || continue;
+
+		# Warn only once, and warn only when one of the bad values are set.
+		# record failure here.
+		if [ ${warned:-0} == 0 ]; then 
+			if [ ${I_KNOW_WHAT_IM_DOING:-0} == 1 ]; then
+				ewarn "Potentially bad ENV values found but I_KNOW_WHAT_IM_DOING=1";
+			else
+				ewarn "Bad ENV values found. Please unset from ENV ( ~/.bashrc, package.env, etc ) or set I_KNOW_WHAT_IM_DOING=1"
+			fi
+			warned=1
+		fi
+
+		# Read ENV Value
+		eval "value=\$$i";
+
+		# Print ENV name/value pair
+		ewarn "    $i=\"$value\"";
+	done
+
+	# If any failures occurred, die unless I_KNOW_WHAT_IM_DOING
+	if [ ${warned:-0} == 1 ] && [ ${I_KNOW_WHAT_IM_DOING:-0} != 1 ]; then
+		die;
+	fi
+}
+