(This is in reference to Testing if your code successfully flocked.)

Notes:

• Proc::Background works in both Windows and Unix. It should work elsewhere, but see its documentation for more information.
• I wrote this to work on Solaris. Linux, apparently, associates the lock with the filehandle and not the file, so this may be unnecessary there.
• The shell-quoting stuff works for me. It may not work for you. If there's a better way to do it, please let me know and I'll update.

use Proc::Background;

my $proc = Proc::Background->new(
    "perl -MFcntl=:flock -e 'open FH, \">>\", \"$filename\";exit flock
+ FH, LOCK_E
X|LOCK_NB",
);

my $rc = $proc->wait >> 8;
ok( !$rc, "Cannot flock $logfile" );
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