Apply suggestion from @mohawk2

Author: mohawk2

Makefile.PL

@@ -114,9 +114,7 @@ sub compileAndRun {
   my ($code) = @_;
   my $result;
 
-  my @inc = shellwords($plplot_include_path);
-  @inc = grep {/^-I/ } @inc;
-  my $inc = join " ", @inc;
+  my $inc = join " ", grep /^-I/, shellwords($plplot_include_path);
 
   check_lib(
     ccflags  => "$plplot_include_path",