--- mummerplot.orig	2017-04-04 12:16:56.000000000 -0700
+++ mummerplot	2018-02-07 12:24:36.000000000 -0800
@@ -881,7 +881,7 @@
         my ($refoff, $reflen, $refdir);
         my ($qryoff, $qrylen, $qrydir);

-        if ( defined (%$rref) ) {
+        if ( %$rref ) {
             #-- skip reference sequence or set atts from hash
             if ( !exists ($rref->{$idR}) ) { next; }
             else { ($refoff, $reflen, $refdir) = @{$rref->{$idR}}; }
@@ -891,7 +891,7 @@
             ($refoff, $reflen, $refdir) = (0, $lenR, 1);
         }

-        if ( defined (%$qref) ) {
+        if ( %$qref ) {
             #-- skip query sequence or set atts from hash
             if ( !exists ($qref->{$idQ}) ) { next; }
             else { ($qryoff, $qrylen, $qrydir) = @{$qref->{$idQ}}; }
@@ -978,7 +978,7 @@
             my ($refoff, $reflen, $refdir);
             my ($qryoff, $qrylen, $qrydir);

-            if ( defined (%$rref) ) {
+            if ( %$rref ) {
                 #-- skip reference sequence or set atts from hash
                 if ( !exists ($rref->{$idR}) ) { next; }
                 else { ($refoff, $reflen, $refdir) = @{$rref->{$idR}}; }
@@ -988,7 +988,7 @@
                 ($refoff, $reflen, $refdir) = (0, $lenR, 1);
             }

-            if ( defined (%$qref) ) {
+            if ( %$qref ) {
                 #-- skip query sequence or set atts from hash
                 if ( !exists ($qref->{$idQ}) ) { next; }
                 else { ($qryoff, $qrylen, $qrydir) = @{$qref->{$idQ}}; }
@@ -1031,7 +1031,7 @@
     }


-    if ( !defined (%$rref) ) {
+    if ( !%$rref ) {
         if ( $ismultiref ) {
             print STDERR
                 "WARNING: Multiple ref sequences overlaid, try -R or -r\n";
@@ -1041,7 +1041,7 @@
         }
     }

-    if ( !defined (%$qref) ) {
+    if ( !%$qref ) {
         if ( $ismultiqry && !$OPT_coverage ) {
             print STDERR
                 "WARNING: Multiple qry sequences overlaid, try -Q, -q or -c\n";