sub f {
    @foo = ( 1, 2 );
    @bar = ( 3, 4 );
    @all = ( \@foo, \@bar );
    return @all;
}

foreach ( f() ) {
    print @{$_};
}

##</code><code>##

sub f {
    @foo = ( 1, 2 );
    @bar = ( 3, 4 );
    return \@foo, \@bar;
}

foreach ( f() ) {
    print @{$_};
}