Announce 5.42 removal of goto to jump into construct

perlfunc: clarify documentation per suggestion from Hugo van der Sanden in
#21601.

Fixes #16275

pod/perldiag.pod

@@ -7664,7 +7664,7 @@ repeatedly, the C</g> has no effect.
 =item Use of "goto" to jump into a construct is deprecated
 
 (D deprecated::goto_construct) Using C<goto> to jump from an outer scope into an inner
-scope is deprecated and should be avoided.
+scope is deprecated and will be removed completely in Perl 5.42.
 
 This was deprecated in Perl 5.12.
 

pod/perlfunc.pod

@@ -3626,7 +3626,8 @@ Also, unlike most named operators, this has the same precedence as
 assignment.
 
 Use of C<goto LABEL> or C<goto EXPR> to jump into a construct is
-deprecated and will issue a warning.  Even then, it may not be used to
+deprecated and will issue a warning; it will become a fatal error in
+Perl 5.42. While still available, it may not be used to
 go into any construct that requires initialization, such as a
 subroutine, a C<foreach> loop, or a C<given>
 block.  In general, it may not be used to jump into the parameter

pp_ctl.c

@@ -3552,7 +3552,9 @@ PP(pp_goto)
                     ? 2
                     : 1;
             if (enterops[i])
-                deprecate(WARN_DEPRECATED__GOTO_CONSTRUCT, "Use of \"goto\" to jump into a construct");
+                deprecate_fatal_in(WARN_DEPRECATED__GOTO_CONSTRUCT,
+                        "5.42",
+                        "Use of \"goto\" to jump into a construct");
         }
 
         /* pop unwanted frames */

t/op/goto.t

@@ -16,7 +16,13 @@ plan tests => 134;
 our $TODO;
 
 my $deprecated = 0;
-local $SIG{__WARN__} = sub { if ($_[0] =~ m/jump into a construct/) { $deprecated++; } else { warn $_[0] } };
+
+local $SIG{__WARN__} = sub {
+    if ($_[0] =~ m/jump into a construct.*?, and will become fatal in Perl 5\.42/) {
+        $deprecated++;
+    }
+    else { warn $_[0] }
+};
 
 our $foo;
 while ($?) {

t/porting/deprecation.t

@@ -103,7 +103,7 @@ if (-e ".git") {
     goto LABEL;
     DONE:
     like($warning,
-        qr/Use of "goto" to jump into a construct is deprecated/,
+        qr/Use of "goto" to jump into a construct is deprecated, and will become fatal in Perl 5\.42/,
         "Got expected deprecation warning");
 }
 # Test that we can silence deprecation warnings with "no warnings 'deprecated'"