patch 8.1.0978: blob not tested with Perl

Problem:    Blob not tested with Perl.
Solution:   Add more test coverage.  Fixes a crash. (Dominique Pelle,
            closes #4037)
diff --git a/src/if_perl.xs b/src/if_perl.xs
index 2655640..099d386 100644
--- a/src/if_perl.xs
+++ b/src/if_perl.xs
@@ -1570,7 +1570,7 @@
     newsv = newSVpv("0z", 2);
     for (i = 0; i < len; i++)
     {
-	sprintf(buf, "%02X", s[i]);
+	sprintf(buf, "%02X", (unsigned char)(s[i]));
 	sv_catpvn(newsv, buf, 2);
     }
     RETVAL = newsv;
diff --git a/src/testdir/test_perl.vim b/src/testdir/test_perl.vim
index 03c5fa0..e24c04f 100644
--- a/src/testdir/test_perl.vim
+++ b/src/testdir/test_perl.vim
@@ -29,6 +29,13 @@
   call assert_equal('abc/def/', getline('$'))
 endfunc
 
+funct Test_VIM_Blob()
+  call assert_equal('0z',         perleval('VIM::Blob("")'))
+  call assert_equal('0z31326162', perleval('VIM::Blob("12ab")'))
+  call assert_equal('0z00010203', perleval('VIM::Blob("\x00\x01\x02\x03")'))
+  call assert_equal('0z8081FEFF', perleval('VIM::Blob("\x80\x81\xfe\xff")'))
+endfunc
+
 func Test_buffer_Delete()
   new
   call setline(1, ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'])
diff --git a/src/version.c b/src/version.c
index 8d22ca9..850c27d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -780,6 +780,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    978,
+/**/
     977,
 /**/
     976,