Weird mark_raw problem with Xslate + wonky workaround

gistfile1.pl

#!/usr/bin/env perl
use strict;
use warnings;
use Text::Xslate qw<mark_raw>;
use 5.010_000;

my $x = Text::Xslate->new(
  function => {
    p => sub {
      return mark_raw( "L(@_)" );
    }
  },
);

# Works:
say $x->render_string('<: p("<a>") :>');
say $x->render_string('<: p("<a>" ~ "foo" ~ "</a>") :>');

# NO WORKY!
say $x->render_string('<: p("<a>" ~ p("foo") ~ "</a>") :>');

# KINDA FIX:
say $x->render_string('<: p( mark_raw("<a>") ~ p("foo") ~ mark_raw("</a>") ) :>');