What if we merged 23922 into blead, then 23782

This branch explores the question:  What if we accept Matt Horsfall's
suggested revision in pp_ctl.c (GH Perl#23922) into blead, then accept the
goto-label-fatal branch underlying p.r. GH Perl#23782 into blead?

Once a couple of merge conflicts were revised, the result would
configure and build but would fail two test files:

  op/goto.t   (Wstat: 0 Tests: 75 Failed: 23)
    Failed tests:  53-75
  uni/labels.t (Wstat: 0 Tests: 11 Failed: 1)
    Failed test:  10

The failures in t/op/goto.t would be not at all surprising.  Those tests
are tests which currently pass in blead but which would fail if the code
changes in pp_ctl.c in 23782 were directly merged into blead.  I first
deleted those tests from t/op/goto.t, then added them back in so that we
would have a tally of the ways in which 'goto LABEL' would *no longer*
work.  So if we first merged 23922, we would presumably re-work those 23
test to pass in an informative way.

I'll need to look further into t/uni/labels.t.

Author: jkeenan

pod/perldiag.pod

@@ -7918,6 +7918,10 @@ For speed and efficiency reasons, Perl internally does not do full
 reference-counting of iterated items, hence deleting such an item in the
 middle of an iteration causes Perl to see a freed value.
 
+=item Use of "goto" to jump into a construct is no longer permitted
+
+(F) More TO COME.
+
 =item Use of /g modifier is meaningless in split
 
 (W regexp) You used the /g modifier on the pattern for a C<split>

t/comp/package_block.t

@@ -1,6 +1,6 @@
 #!./perl
 
-print "1..7\n";
+print "1..5\n";
 
 $main::result = "";
 eval q{
@@ -56,37 +56,4 @@ eval q{
 };
 print $main::result eq "a(2)b(4)c(6)d(8)e(10)f(12)" ? "ok 5\n" : "not ok 5\n";
 
-$main::result = "";
-$main::warning = "";
-$SIG{__WARN__} = sub { $main::warning .= $_[0]; };
-eval q{
-    $main::result .= "a(".__PACKAGE__."/".eval("__PACKAGE__").")";
-    goto l0;
-    $main::result .= "b(".__PACKAGE__."/".eval("__PACKAGE__").")";
-    package Foo {
-	$main::result .= "c(".__PACKAGE__."/".eval("__PACKAGE__").")";
-	l0:
-	$main::result .= "d(".__PACKAGE__."/".eval("__PACKAGE__").")";
-	goto l1;
-	$main::result .= "e(".__PACKAGE__."/".eval("__PACKAGE__").")";
-    }
-    $main::result .= "f(".__PACKAGE__."/".eval("__PACKAGE__").")";
-    l1:
-    $main::result .= "g(".__PACKAGE__."/".eval("__PACKAGE__").")";
-    goto l2;
-    $main::result .= "h(".__PACKAGE__."/".eval("__PACKAGE__").")";
-    package Bar {
-	l2:
-	$main::result .= "i(".__PACKAGE__."/".eval("__PACKAGE__").")";
-    }
-    $main::result .= "j(".__PACKAGE__."/".eval("__PACKAGE__").")";
-};
-print $main::result eq
-	"a(main/main)d(Foo/Foo)g(main/main)i(Bar/Bar)j(main/main)" ?
-    "ok 6\n" : "not ok 6\n";
-print $main::warning =~ /\A
-	Use\ of\ "goto"\ [^\n]*\ line\ 3\.\n
-	Use\ of\ "goto"\ [^\n]*\ line\ 15\.\n
-    \z/x ? "ok 7\n" : "not ok 7\n";
-
 1;

t/op/eval.t

@@ -224,13 +224,13 @@ is(do {
 #   (BUG ID 20010305.003 (#5963))
 {
     eval {
-	eval { goto foo; };
-	like($@, qr/Can't "goto" into the middle of a foreach loop/,
-	     'eval catches bad goto calls');
-	last;
-	foreach my $i (1) {
-	    foo: fail('jumped into foreach');
-	}
+        eval { goto foo; };
+        like($@, qr/Can't "goto" into the middle of a foreach loop/,
+             'eval catches bad goto calls');
+        last;
+        foreach my $i (1) {
+            foo: fail('jumped into foreach');
+        }
     };
     fail("Outer eval didn't execute the last");
     diag($@);