Index: perl-module.eclass
===================================================================
RCS file: /var/cvsroot/gentoo-x86/eclass/perl-module.eclass,v
retrieving revision 1.163
diff -u -B -r1.163 perl-module.eclass
--- perl-module.eclass	14 Mar 2015 14:32:10 -0000	1.163
+++ perl-module.eclass	15 Mar 2015 13:22:48 -0000
@@ -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 +550,53 @@
 		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 tell the user what needs to be unset.
+# There's a workaround, but you'll have to read the code for it.
+perl_check_env() {
+	local errored value;
+
+	for i in PERL_MM_OPT PERL5LIB PERL5OPT PERL_MB_OPT PERL_CORE PERLPREFIX; do
+		# Next unless match
+		[ -v $i ] || continue;
+
+		# Warn only once, and warn only when one of the bad values are set.
+		# record failure here.
+		if [ ${errored:-0} == 0 ]; then
+			if [ -n ${I_KNOW_WHAT_I_AM_DOING} ]; then
+				elog "perl-module.eclass: Suspicious environment values found.";
+			else
+				eerror "perl-module.eclass: Suspicious environment values found.";
+			fi
+		fi
+		errored=1
+
+		# Read ENV Value
+		eval "value=\$$i";
+
+		# Print ENV name/value pair
+		if [ -n ${I_KNOW_WHAT_I_AM_DOING} ]; then
+			elog "    $i=\"$value\"";
+		else
+			eerror "    $i=\"$value\"";
+		fi
+	done
+
+	# Return if there were no failures
+	[ ${errored:-0} == 0 ] && return;
+
+	# Return if user knows what they're doing
+	if [ -n ${I_KNOW_WHAT_I_AM_DOING} ]; then
+		elog "Continuing anyway, seems you know what you're doing."
+		return
+	fi
+
+	eerror "Your environment settings may lead to undefined behavior and/or build failures."
+	die "Please fix them ( ~/.bashrc, package.env, ... )."
+}