Here's an approach that reduces the number of file-opening calls you need to manage --- determine what flags you want on the file handle and use sysopen once. In the following modes 1 and 2 act like > and >> respectively, else the file is opened read-only. This can be altered --- if you'd rather fail on attempting to append to a non-existing file, remove the O_CREAT flag from mode 2 for example.

use Fcntl qw(:DEFAULT :flock);
# assume $flock_enabled set accordingly

sub safe_open {
    my $fn = shift;
    $fn =~ s/^(>>?)//;
    $mode = length($1);
    my $flags = $mode == 1 ? O_CREAT | O_WRONLY | O_TRUNC  :
                $mode == 2 ? O_CREAT | O_WRONLY | O_APPEND :
                O_RDONLY;
    sysopen(my $fh, $fn, $flags) || die "Can't open $fn: $!";
    flock($fh, LOCK_EX) || die "Can't flock $fn: $!" if $flock_enabled
+;
    return $fh;
}
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