https://rt.cpan.org/Public/Bug/Display.html?id=108434

diff -Nur Proc-PID-File-1.27.old/File.pm Proc-PID-File-1.27/File.pm
--- Proc-PID-File-1.27.old/File.pm	2009-10-13 06:40:21.000000000 +0500
+++ Proc-PID-File-1.27/File.pm	2016-04-28 16:53:48.800782841 +0400
@@ -283,7 +283,8 @@
 		|| die qq/Cannot open pid file "$self->{path}": $!\n/;
 	flock($fh, LOCK_EX | LOCK_NB)
         || die qq/pid "$self->{path}" already locked: $!\n/;
-	my ($pid) = <$fh> =~ /^(\d+)/;
+	my $maybe = <$fh>;
+	my ($pid) = $maybe =~ /^(\d+)/ if (defined $maybe);
 	close $fh if @_ == 1;
 
 	$self->debug("read(\"$self->{path}\") = " . ($pid || ""));