+ open DEBUG, ">&STDERR" or die $!;
+ DEBUG->autoflush(1);
+ $debuglevel ||= 1;
+}
+
+sub enabledebuglevel ($) {
+ my ($newlevel) = @_; # may be undef (eg from env var)
+ die if $debuglevel;
+ $newlevel //= 0;
+ $newlevel += 0;
+ return unless $newlevel;
+ $debuglevel = $newlevel;
+ enabledebug();