MDEV-19821 "perl;" snippet must run the same perl executable that runs mtr.

client/mysqltest.cc

@@ -4643,8 +4643,16 @@ void do_perl(struct st_command *command)
 
     str_to_file(temp_file_path, ds_script.str, ds_script.length);
 
+    /* Use the same perl executable as the one that runs mysql-test-run.pl */
+    const char *mtr_perl=getenv("MTR_PERL");
+    if (!mtr_perl)
+      mtr_perl="perl";
+
     /* Format the "perl <filename>" command */
-    my_snprintf(buf, sizeof(buf), "perl %s", temp_file_path);
+    if (strchr(mtr_perl, ' '))
+      my_snprintf(buf, sizeof(buf), "\"%s\" %s", mtr_perl, temp_file_path);
+    else
+      my_snprintf(buf, sizeof(buf), "%s %s", mtr_perl, temp_file_path);
 
     if (!(res_file= my_popen(buf, "r")))
     {

mysql-test/mysql-test-run.pl

@@ -366,6 +366,8 @@ main();
 
 
 sub main {
+  $ENV{MTR_PERL}=$^X;
+
   # Default, verbosity on
   report_option('verbose', 0);