The limit of if is encountered if you declare a variable.

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

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

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

• Declare the var earlier:

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

  my $y;
  if (($y) = f($x)) {   # Returns () on error.
     ...
  }
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• Save the result:

  my $success = open(my $fh, '<', $qfn);
  if (!$success) {
     ...
  }
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  my $success = my ($y) = f($x);  # Returns () on error.
  if (!$success) {
     ...
  }
  [download]

• Use do:

  open(my $fh, '<', $qfn)
     or do { ...
           };
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  my ($y) = f($x)   # Returns () on error.
     or do { ...
           };
  [download]