--- /dev/null
+#!/usr/bin/perl -w
+
+# Test that env vars are honoured.
+
+use strict;
+use lib 't/lib';
+
+use Test::More (
+ $^O eq 'VMS'
+ ? ( skip_all => 'VMS' )
+ : ( tests => 1 )
+);
+
+use Test::Harness;
+
+# HARNESS_PERL_SWITCHES
+
+my $test_template = <<'END';
+#!/usr/bin/perl
+
+use Test::More tests => 1;
+
+is $ENV{HARNESS_PERL_SWITCHES}, '-w';
+END
+
+open TEST, ">env_check_t.tmp";
+print TEST $test_template;
+close TEST;
+
+END { unlink 'env_check_t.tmp'; }
+
+{
+ local $ENV{HARNESS_PERL_SWITCHES} = '-w';
+ my ( $tot, $failed )
+ = Test::Harness::execute_tests( tests => ['env_check_t.tmp'] );
+ is $tot->{bad}, 0;
+}
+
+1;