When setting environment variables in the atrun script, use the

"export foo=bar" form instead of "foo=bar; export foo" since the
former allows the shell to catch variable names that are not valid
shell identifiers.  This will cause /bin/sh to exit with an error
(which gets mailed to the at user) and it will not run the script.

Obtained from:	OpenBSD (r1.63 millert)
MFC after:	3 days

usr.bin/at/at.c

@@ -367,6 +367,7 @@ writefile(time_t runtimer, char queue)
 
 	if (export)
 	{
+	    (void)fputs("export ", fp);
 	    fwrite(*atenv, sizeof(char), eqp-*atenv, fp);
 	    for(ap = eqp;*ap != '\0'; ap++)
 	    {
@@ -389,7 +390,6 @@ writefile(time_t runtimer, char queue)
 		    fputc(*ap, fp);
 		}
 	    }
-	    fputs("; export ", fp);
 	    fwrite(*atenv, sizeof(char), eqp-*atenv -1, fp);
 	    fputc('\n', fp);