Here you go

--- old\lib\WWW\Mechanize.pm        2021-04-27 18:52:56.406250000 -070
+0
+++ new\lib\WWW\Mechanize.pm        2021-04-27 18:52:20.046875000 -070
+0
@@ -1435,6 +1435,7 @@
     iframe => 'src',
     link   => 'href',
     meta   => 'content',
+    base   => 'href',
 );

 sub _extract_links {
@@ -1512,6 +1513,9 @@

     my $text;
     my $name;
+    if( $tag eq 'base' ){
+        $self->{base} = $token->[1]{href} ;
+    }
     if ( $tag eq 'a' ) {
         $text = $parser->get_trimmed_text("/$tag");
         $text = '' unless defined $text;
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