Since IO::Socket::UNIX is part of core perl, it's not enough to

"eval use" it. Instead trap the error that occurs when creating the socket
on platforms that does not support it. 

mysql-test/lib/My/Platform.pm

@@ -51,15 +51,6 @@ BEGIN {
   }
 }
 
-BEGIN {
-  if (eval "use IO::Socket::UNIX; 1") {
-    eval 'sub HAVE_UNIX_SOCKET { 1 }';
-  }
-  else {
-    eval 'sub HAVE_UNIX_SOCKET { 0 }';
-  }
-}
-
 
 #
 # native_path
@@ -105,27 +96,27 @@ sub check_socket_path_length {
   my ($path)= @_;
   my $truncated= 0;
 
-  if (HAVE_UNIX_SOCKET){
-    require IO::Socket::UNIX;
-
-    my $sock = new IO::Socket::UNIX
-    (
-     Local => $path,
-     Listen => 1,
-    ) or die $!;
-    if ($path ne $sock->hostpath()){
-      # Path was truncated
-      $truncated= 1;
-      # Output diagnostic messages
-      print "path: '$path', length: ", length($path) ,"\n";
-      print "hostpath: '", $sock->hostpath(),
-	"', length: ", length($sock->hostpath()), "\n";
-    }
-    $sock= undef;
-    unlink($path);
-    return $truncated;
-  };
-  # All paths OK!
+  require IO::Socket::UNIX;
+
+  my $sock = new IO::Socket::UNIX
+  (
+   Local => $path,
+   Listen => 1,
+  );
+  if (!defined $sock){
+    # Could not create a UNIX domain socket
+    return 0; # Ok, will not be used by mysqld either    
+  }
+  if ($path ne $sock->hostpath()){
+    # Path was truncated
+    $truncated= 1;
+    # Output diagnostic messages
+    print "path: '$path', length: ", length($path) ,"\n";
+    print "hostpath: '", $sock->hostpath(),
+	  "', length: ", length($sock->hostpath()), "\n";
+  }
+  $sock= undef; # Close socket
+  unlink($path); # Remove the physical file
   return $truncated;
 }