Small fix.

src/lib/Sympa/WWW/Tools.pm

@@ -242,7 +242,7 @@ sub get_robot {
     my $request_path = $org_script_name . $org_path_info;
 
     # Find mail domain (a.k.a. "robot") of which web URL matches script-URI.
-    my ($robot_id, $script_path) = (undef, '');
+    my ($robot_id, $script_path) = (undef, undef);
     foreach my $rid (Sympa::List::get_robots()) {
         my $local_url;
         foreach my $key (@keys) {
@@ -266,15 +266,16 @@ sub get_robot {
             and grep { $uri->scheme eq $_ } qw(http https);
 
         my $host = lc URI::Escape::uri_unescape($uri->host // '');
-        my $path = URI::Escape::uri_unescape($uri->path // '/');
+        my $path = URI::Escape::uri_unescape($uri->path // '');
         next unless $request_host eq $host;
         next
             unless $request_path eq $path
-            or 0 == index($request_path, $path . '/');
+            or 0 == index $request_path, $path . '/';
 
         # The longest path wins.
         ($robot_id, $script_path) = ($rid, $path)
-            if length $script_path < length $path;
+            if not defined $script_path
+            or length $script_path < length $path;
     }
 
     return unless $robot_id;

t/WWW_Tools.t

@@ -73,5 +73,21 @@ $ENV{PATH_INFO}   = 'help';
 is_deeply [Sympa::WWW::Tools::get_robot('wwsympa_url')], [],
     'dubious PATH_INFO';
 
+$Conf::Conf{wwsympa_url} = 'http://web.example.org';
+
+$ENV{SERVER_NAME} = 'web.example.org';
+$ENV{SCRIPT_NAME} = '';
+$ENV{PATH_INFO}   = '/help';
+is_deeply [Sympa::WWW::Tools::get_robot('wwsympa_url')],
+    ['mail.example.org', '', '/help'],
+    'URL prefix on the top: (empty) SCRIPT_NAME & non-empty PATH_INFO';
+
+$ENV{SERVER_NAME} = 'web.example.org';
+$ENV{SCRIPT_NAME} = '/help';
+$ENV{PATH_INFO}   = undef;
+is_deeply [Sympa::WWW::Tools::get_robot('wwsympa_url')],
+    ['mail.example.org', '', '/help'],
+    'URL prefix on the top: no PATH_INFO';
+
 done_testing();
 rmtree 't/tmp';