Allow dots in the names, bug #95173.  Patch by Kerin Millar.
Re-sourced for 2.28.2

--- debianutils-2.28.2/run-parts.8
+++ debianutils-2.28.2/run-parts.8
@@ -27,7 +27,8 @@
 
 If neither the \-\-lsbsysinit option nor the \-\-regex option is given
 then the names must consist entirely of upper and lower case letters,
-digits, underscores, and hyphens.                           
+digits, underscores, hyphens, and periods. However, the name must not begin
+with a period.
                                                                                 
 If the \-\-lsbsysinit option is given, then the names must not end
 in .dpkg\-old  or .dpkg\-dist or .dpkg\-new or .dpkg\-tmp, and must
--- debianutils-2.28.2/run-parts.c
+++ debianutils-2.28.2/run-parts.c
@@ -494,7 +494,7 @@ regex_compile_pattern (void)
                     != 0)
             pt_regex = &tradre;
 
-    } else if ( (err = regcomp(&classicalre, "^[a-zA-Z0-9_-]+$",
+    } else if ( (err = regcomp(&classicalre, "^[a-zA-Z0-9_-][a-zA-Z0-9._-]+$",
                     REG_EXTENDED | REG_NOSUB)) != 0)
         pt_regex = &classicalre;