Bug#27753 enable mysql-test-run.pl to ignore tests based on wildcard

 - Fix problem in first implementation

mysql-test/lib/mtr_cases.pl

@@ -32,16 +32,14 @@ my $skip_test;
 
 sub init_pattern {
   my ($from, $what)= @_;
-  if ( $from =~ /[a-z0-9]/ ) {
+  if ( $from =~ /^[a-z0-9]$/ ) {
     # Does not contain any regex, make the pattern match
     # beginning of string
     $from= "^$from";
   }
-  else {
   # Check that pattern is a valid regex
   eval { "" =~/$from/; 1 } or
     mtr_error("Invalid regex '$from' passed to $what\nPerl says: $@");
-  }
   return $from;
 }