diff --git a/t/x09.pl b/t/x09.pl
index 8967835..e700107 100755
--- a/t/x09.pl
+++ b/t/x09.pl
@@ -94,17 +94,6 @@ sub polar {
 #  plFree2dGrid ($cgrid2);
 }
 
-# f2mnmx
-#
-# Returns min & max of input 2d array
-
-sub f2mnmx {
-  my $f = shift;
-  my $fmin = min ($f);
-  my $fmax = max ($f);
-  return ($fmin, $fmax)
-}
-
 # Shielded potential contour plot example
 
 sub potential {
@@ -122,8 +111,8 @@ sub potential {
 
   my $rmax = 0.5 + (PRPTS - 1);
 
-  my ($xmin, $xmax) = f2mnmx ($xg);
-  my ($ymin, $ymax) = f2mnmx ($yg);
+  my ($xmin, $xmax) = minmax($xg);
+  my ($ymin, $ymax) = minmax($yg);
 
   my $x0 = ($xmin + $xmax) / 2;
   my $y0 = ($ymin + $ymax) / 2;
@@ -161,7 +150,7 @@ sub potential {
   my $div2i = sqrt (($xg - $d2i) ** 2 + ($yg + $d2i) ** 2 + $eps ** 2);
   my $z = $q1 / $div1 + $q1i / $div1i + $q2 / $div2 + $q2i / $div2i;
 
-  my ($zmin, $zmax) = f2mnmx ($z);
+  my ($zmin, $zmax) = minmax($z);
 
   # Positive and negative contour levels
 
diff --git a/t/x15.pl b/t/x15.pl
index 822c2d6..dead6d6 100755
--- a/t/x15.pl
+++ b/t/x15.pl
@@ -37,7 +37,6 @@
 
 sub plot1 ();
 sub plot2 ();
-sub f2mnmx ($);
 sub cmap1_init1	();
 sub cmap1_init2	();
 
@@ -78,7 +77,7 @@ sub main {
 	}
     }
 
-    ($zmin, $zmax) = f2mnmx ($z);
+    ($zmin, $zmax) = minmax($z);
 
     plot1 ();
     plot2 ();
@@ -283,13 +282,4 @@ ()
     
 }
 
-# f2mnmx
-#
-# Returns min & max of input 2d array
-
-sub f2mnmx ($) {
-    my $f = shift;
-    return (min ($f), max ($f));
-}
-
 main ();
diff --git a/t/x22.pl b/t/x22.pl
index 07de8fe..89a4eba 100755
--- a/t/x22.pl
+++ b/t/x22.pl
@@ -121,18 +121,10 @@ sub transform {
 # Vector plot of flow through a constricted pipe
 # with a coordinate transform
 sub constriction2 {
-    my $nx = nx;
-    my $ny = ny;
-    my $nc   = 11;
-    my $nseg = 20;
-
-    my $dx = 1.0;
-    my $dy = 1.0;
-
-    my $xmin = -$nx / 2 * $dx;
-    my $xmax = $nx / 2 * $dx;
-    my $ymin = -$ny / 2 * $dy;
-    my $ymax = $ny / 2 * $dy;
+    my ($nx, $ny, $nc, $nseg) = (nx, ny, 11, 20);
+    my ($dx, $dy) = (1.0, 1.0);
+    my ($xmin, $xmax) = (-$nx / 2 * $dx, $nx / 2 * $dx);
+    my ($ymin, $ymax) = (-$ny / 2 * $dy, $ny / 2 * $dy);
 
     plstransform( \&transform, $xmax );
 
@@ -163,13 +155,6 @@ sub constriction2 {
     plstransform( undef, undef );
 }
 
-sub f2mnmx {
-  my $f = shift;
-  my $fmin = min ($f);
-  my $fmax = max ($f);
-  return ($fmin, $fmax);
-}
-
 # Vector plot of the gradient of a shielded potential (see example 9)
 
 sub potential {
@@ -199,7 +184,6 @@ sub potential {
                (0.5 + sequence (ntheta)))->dummy (0, nr);
   my $x = $r * cos ($theta);
   my $y = $r * sin ($theta);
-  my $cgrid2 = plAlloc2dGrid ($x, $y);
   my $div1 = sqrt (($x - $d1) ** 2 + ($y - $d1) ** 2 + $eps * $eps);
   my $div1i = sqrt (($x - $d1i) ** 2 + ($y - $d1i) ** 2 + $eps * $eps);
   my $div2 = sqrt (($x - $d2) ** 2 + ($y + $d2) ** 2 + $eps * $eps);
@@ -210,9 +194,9 @@ sub potential {
   my $v = -$q1 * ($y - $d1) / ($div1**3) - $q1i * ($y - $d1i) / ($div1i ** 3)
           -$q2 * ($y + $d2) / ($div2**3) - $q2i * ($y + $d2i) / ($div2i ** 3);
 
-  my ($xmin, $xmax) = f2mnmx ($x);
-  my ($ymin, $ymax) = f2mnmx ($y);
-  my ($zmin, $zmax) = f2mnmx ($z);
+  my ($xmin, $xmax) = minmax($x);
+  my ($ymin, $ymax) = minmax($y);
+  my ($zmin, $zmax) = minmax($z);
 
   plenv ($xmin, $xmax, $ymin, $ymax, 0, 0);
   pllab ("(x)", "(y)",
@@ -224,6 +208,7 @@ sub potential {
 
   plcol0 (3);
   pllsty (2);
+  my $cgrid2 = plAlloc2dGrid ($x, $y);
   plcont ($z, 1, nr, 1, ntheta, $clevel, \&pltr2, $cgrid2);
   pllsty (1);
   plcol0 (1);