#!/usr/bin/perl -w
use strict;
use Fcntl qw(:DEFAULT :seek);
use 5.10.0;

our @extraoptions = ();
my %fh;

my $str = "#push \@extraoptions, '--bvtonly';\npush \@extraoptions, '--debug';warn 'included by eval'";

1 && eval($str);
print "eval error - '$@'\n";

doit();
exit;

sub doit {
        my $file = '/tmp/z';
        say "lock says: ".(lockf($file) // "UNDEFINED - $!");
        say "unlock says: ".(unlockf($file) // "UNDEFINED - $!");
}
sub lockf {
        my $version = shift;
        open $fh{$version}, ">>$version" or die;
        my $flags = pack('sslli', F_WRLCK, SEEK_SET, 0, 0);# struct flock from fcntl - flock doesn't work on NFS
        return fcntl($fh{$version}, F_SETLK, $flags);
}

sub unlockf {
        my $version = shift;
        if($fh{$version}){
                my $flags = pack('sslli', F_UNLCK, SEEK_SET, 0, 0);# struct flock from fcntl - flock doesn't work on NFS
                my $ret= fcntl($fh{$version}, F_SETLK, $flags);
                delete $fh{$version};
                return $ret;
        }else{
                die "Cannot release lock I don't hold for $version!";
        }
}