if (!open(my $fh, '<', $qfn)) {
   ...
}

print $fh $s;  # XXX

##</code><code>##

if (my ($y) = f($x)) {   # Returns () on error.
   ...
}

print defined($y) ? $y : '[undef]';  # XXX

##</code><code>##

my $fh;
if (!open($fh, '<', $qfn)) {
   ...
}

##</code><code>##

my $y;
if (($y) = f($x)) {   # Returns () on error.
   ...
}

##</code><code>##

my $success = open(my $fh, '<', $qfn);
if (!$success) {
   ...
}

##</code><code>##

my $success = my ($y) = f($x);  # Returns () on error.
if (!$success) {
   ...
}

##</code><code>##

open(my $fh, '<', $qfn)
   or do { ...
         };

##</code><code>##

my ($y) = f($x)   # Returns () on error.
   or do { ...
         };