Use homebrew perl to run cpanm

cpanm needs to be run with the version of perl we want to install
the modules into. For macOS, attempt to detect where cpanm is
located and ensure it is run with the version of perl on the path.

Author: cpeel

install_cpan_modules.pl

@@ -27,7 +27,28 @@
     push @modules, "Win32::Unicode::Process";
 }
 
+# Command to use to run cpanm, default to the command directly
+$cpanm = "cpanm";
+
+# On Mac, we want to run cpanm with the version of perl on the path -- which
+# should be the homebrew-installed version -- not whatever version cpanm is
+# pointing to which might be the one that came with macOS.
+if ( $^O eq 'darwin' ) {
+
+    # Intel
+    if ( -e "/usr/local/bin/cpanm" ) {
+        $cpanm = "perl /usr/local/bin/cpanm";
+    }
+
+    # Apple Silicon
+    elsif ( -e "/opt/homebrew/bin/cpanm" ) {
+        $cpanm = "perl /opt/homebrew/bin/cpanm";
+    }
+
+    # fall-through to using cpanm directly
+}
+
 foreach my $module (@modules) {
-    system("cpanm --notest $module") == 0
+    system("$cpanm --notest $module") == 0
       or die("Failed trying to install $module\n");
 }