diff --git a/lib/Math/Round/Fair.pm b/lib/Math/Round/Fair.pm
index 262b789..3136341 100644
--- a/lib/Math/Round/Fair.pm
+++ b/lib/Math/Round/Fair.pm
@@ -12,13 +12,15 @@ our $VERSION = '0.01_01';
 
 our @EXPORT_OK = qw/round_fair round_adjacent/;
 
-our $debug;
 BEGIN {
+    my $debug;
+    sub DEBUG { $debug }
+
     $debug = $ENV{MATH_ROUND_FAIR_DEBUG} || 0;
-    use Devel::Assert $debug ? ('-all -verbose') : ();
+    use Devel::Assert DEBUG() ? ('-all -verbose') : ();
 
     # used in assertions
-    eval q{use Perl6::Junction 'none'} if $debug;
+    eval q{use Perl6::Junction 'none'} if DEBUG();
 }
 
 
@@ -230,8 +232,8 @@ sub _round_adjacent_core {
         # See bottom of file for proof of this property:
         assert($tslack + $eps >= $p0 * (1.0 - $p0));
 
-        # wrapped in assert to make it a noop when $debug == 0
-        assert(do { warn "TSLACK = $tslack\n" if $debug > 1; 1 });
+        # wrapped in assert to make it a noop when DEBUG() == 0
+        assert(do { warn "TSLACK = $tslack\n" if DEBUG() > 1; 1 });
 
         if ( $tslack > $eps1 ) {
             $eps += 128.0 * $eps1 * $eps / $tslack;
@@ -295,7 +297,7 @@ sub _adjust_input {
 sub _check_invariants {
     my ( $eps, $v, $fp ) = @_;
 
-    if ( $debug > 1 ) {
+    if ( DEBUG() > 1 ) {
         warn sprintf "%d %f\n", floor($_), $_ for @$fp;
     }
 
diff --git a/t/01-round_fair.t b/t/01-round_fair.t
index a4e011e..ac34e90 100644
--- a/t/01-round_fair.t
+++ b/t/01-round_fair.t
@@ -6,7 +6,7 @@ use List::Util qw/sum min max/;
 
 BEGIN { use_ok 'Math::Round::Fair', qw/round_fair/ }
 
-ok $Math::Round::Fair::debug, 'assertions enabled for tests';
+ok Math::Round::Fair::DEBUG(), 'assertions enabled for tests';
 
 my $to_allocate = 7;
 my @weights = (1) x 10;
diff --git a/t/10-nearest.t b/t/10-nearest.t
index 3c7d493..913743f 100644
--- a/t/10-nearest.t
+++ b/t/10-nearest.t
@@ -6,8 +6,8 @@ $^W=1;
 use Test;
 BEGIN { plan tests => 6, todo => [] }
 
+BEGIN { $ENV{MATH_ROUND_FAIR_DEBUG} = 1 }
 use Math::Round::Fair qw(round_adjacent);
-$Math::Round::Fair::debug = 1;
 
 srand(0);
 my @result = round_adjacent();
diff --git a/t/11-random.t b/t/11-random.t
index 2221c92..aba1622 100644
--- a/t/11-random.t
+++ b/t/11-random.t
@@ -21,9 +21,9 @@ BEGIN {
 	plan tests => $cases, todo => [];
 }
 
+BEGIN { $ENV{MATH_ROUND_FAIR_DEBUG} = 0 }
 use Check_FairRound;
 use Math::Round::Fair;
-$Math::Round::Fair::debug = 0;
 
 sub gen_test_case {
  	my $n = rand(4)<1 ? 1 : (rand(3)<1 ? 2 : 1+int(rand(10)));
diff --git a/t/12-random_big.t b/t/12-random_big.t
index 7ff9e4b..758b612 100644
--- a/t/12-random_big.t
+++ b/t/12-random_big.t
@@ -21,9 +21,9 @@ BEGIN {
 	plan tests => $cases, todo => [];
 }
 
+BEGIN { $ENV{MATH_ROUND_FAIR_DEBUG} = 1 }
 use Check_FairRound;
 use Math::Round::Fair;
-$Math::Round::Fair::debug = 1;
 
 sub gen_test_case {
  	my $n = 5+int(rand(50));
diff --git a/t/99-pod_spelling.t b/t/99-pod_spelling.t
index 0acfb2a..8e34ae3 100644
--- a/t/99-pod_spelling.t
+++ b/t/99-pod_spelling.t
@@ -18,4 +18,5 @@ all_pod_files_spelling_ok();
 __DATA__
 Marc
 Mims
+runtime
 situ