That just means that lexically scoped subs can't yet be defined that way. What you probably mean is:

sub save_friend_info {
    # . . .
}
[download]

You can have a lexical sub, but you need to assign it to an ordinary scalar:

{
    my $save_friend_info = sub {
        # . . .
    };
    
    $save_friend_info->(@args) or die $!;
}
[download]