support first argument of markdown as blessed string like Text::Xslate::Type::Raw.

Makefile.PL

@@ -15,6 +15,7 @@ perl_version    '5.008';
 requires        'Digest::MD5'     => undef;
 requires        'Text::Balanced'  => undef;
 requires        'Encode'          => undef;
+requires        'Scalar::Util'    => undef;
 test_requires  'Test::More'      => '0.42';
 test_requires  'Test::Exception' => undef;
 test_requires  'List::MoreUtils' => undef;

lib/Text/Markdown.pm

@@ -7,6 +7,7 @@ use re 'eval';
 use Digest::MD5 qw(md5_hex);
 use Encode      qw();
 use Carp        qw(croak);
+use Scalar::Util qw(blessed);
 use base        'Exporter';
 
 our $VERSION   = '1.000031'; # 1.0.31
@@ -186,7 +187,7 @@ sub markdown {
     my ( $self, $text, $options ) = @_;
 
     # Detect functional mode, and create an instance for this run
-    unless (ref $self) {
+    unless (blessed($self) && $self->isa('Text::Markdown')) {
         if ( $self ne __PACKAGE__ ) {
             my $ob = __PACKAGE__->new();
                                 # $self is text, $text is options

t/50blessed-string.t

@@ -0,0 +1,26 @@
+use strict;
+use warnings;
+use utf8;
+use Test::More;
+use Text::Markdown qw(markdown);
+
+plan tests => 1;
+
+{
+    # emulate class like Text::Xslate::Type::Raw
+    package    #
+      StringClass;
+
+    use overload (
+        q{""} => sub { ${ $_[0] } },
+        fallback => 1,
+    );
+    sub new {
+        my ($class, $str) = @_;
+        bless \$str, $class;
+    }
+}
+
+my $src = StringClass->new('foo');
+is(markdown($src), "<p>foo</p>\n");
+