use strict;
my %locks;

while (chomp(my $line = <STDIN>)) {
    next unless ($line =~ /Mutex(.*)::(.*)/);
    my ($mutex,$action) = ($1,$2);

    if ($action eq 'locking') {
        if ($locks{$mutex}) {
            printf ("Mutex %s already locked on line %d, locked again 
+on line %d\n",
                $mutex, $locks{$mutex}, $.);
        } else {
            $locks{$mutex} = $.;
        }
    } elsif ($action eq 'unlocked') {
        if ($locks{$mutex}) {
            delete $locks{$mutex};
        } else {
            printf ("Mutex %s unlocked on line %d, but wasn't locked.\
+n",
                $mutex, $.);
        }
    }
}

foreach my $mutex (keys %locks) {
    printf ("Mutex %s locked on line %d, but wasn't unlocked\n",
        $mutex, $locks{$mutex});
}
[download]