$ perl -le'undef $_; defined $_->{0}; print $_'
HASH(0x813f1c8)

##</code><code>##

while( defined $bros->{ $find }->[ $index ]->{ $key } ) {
    # ...
}

##</code><code>##

while(
    ref $bros->{ $find }->[ $index ]
    and defined $bros->{ $find }->[ $index ]->{ $key }
) {
    # ...
}

##</code><code>##

for my $year ( qw( 1958 1959 1960 1961 1962 1963 1964 ) ) {
	for my $film ( @{ $bros->{ $year } } ) {
		push @res, { brother => $film, year => $year }
			if $film->{ $key } =~ /$data/i;
	}
}

##</code><code>##

for my $year ( qw( 1958 1959 1960 1961 1962 1963 1964 ) ) {
	push @res, (
		map +{ brother => $_, year => $year }, 
		grep $_->{ $key } =~ /$data/i,
		@{ $bros->{ $year } },
	);
}