Created attachment 1450492 [details]
Fix for unescaped left brace

I am preparing upgrade to Perl 5.28. texinfo's tests fail during local rebuild with following errors:

diff -a -u -r formatting//diffs/staging_res/texi_cond/cond.2 formatting//out_parser/texi_cond/cond.2
--- formatting//diffs/staging_res/texi_cond/cond.2	2017-08-27 12:45:45.000000000 +0200
+++ formatting//out_parser/texi_cond/cond.2	2018-06-12 13:55:29.742494430 +0200
@@ -0,0 +1,2 @@
+Unescaped left brace in regex is deprecated here (and will be fatal in Perl 5.32), passed through in regex; marked by <-- HERE in m/^\s+@([[:alnum:]][[:alnum:]\-]*)({ <-- HERE })?\s*/ at ../../tp/Texinfo/Parser.pm line 5481.
+Unescaped left brace in regex is deprecated here (and will be fatal in Perl 5.32), passed through in regex; marked by <-- HERE in m/^\s+@([[:alnum:]][[:alnum:]\-]*)({ <-- HERE })?\s*(\@(c|comment)((\@|\s+).*)?)?/ at ../../tp/Texinfo/Parser.pm line 5485.

It is related to this change
https://metacpan.org/pod/release/XSAWYERX/perl-5.28.0-RC2/pod/perldelta.pod#Use-of-unescaped-%22%7B%22-immediately-after-a-%22(%22-in-regular-expression-patterns

The proposed fixed is attached. Verified with Perl 5.28 RC1.