Perl is making a guess and treating this C<exec> as a request to
terminate the Perl script and execute the specified command.
+=item internal %<num>p might conflict with future printf extensions
+
+(S internal) Perl's internal routine that handles C<printf> and C<sprintf>
+formatting follows a slightly different set of rules when called from
+C or XS code. Specifically, formats consisting of digits followed
+by "p" (e.g., "%7p") are reserved for future use. If you see this
+message, then an XS module tried to call that routine with one such
+reserved format.
+
=item Internal urp in regex; marked by <-- HERE in m/%s/
(P) Something went badly awry in the regular expression parser. The
Illegal character %sin prototype for %s : %s
Illegal hexadecimal digit '%c' ignored
Illegal octal digit '%c' ignored
-internal %<num>p might conflict with future printf extensions
Invalid argument to sv_cat_decode
Invalid range "%c-%c" in transliteration operator
Invalid separator character %c%c%c in PerlIO layer specification %s