Another way to look at this issue is that a subroutine is a logical entity representing one conceptual block. This means that if a statement (or group of statements) is conceptually one action, it should be a sub. If it is conceptually two actions, it should be two subs. And, so on.

Thus, for example, you often see print_header() and print_footer() in CGI scripts. What this does is group together the print statements that make up the header. The average reader doesn't care what goes into the header when s/he is reading the program flow. If s/he cares, then s/he can go into that function and concentrate on the action of printing the header, without getting distracted by anything else.

Now, one thing I would be careful of is over-compartmentalizing. One thing I hate about reading other people's OO code is that I have to trace 10 function calls just to find out who's doing what. Usually, this is in 10 different files, to boot! I would very much reccomend thinking about generic functions. For example:

sub get {
    my $self = shift;
    my ($attr_name) = @_;

    if(exists $self->{$attr_name}) {
        return $self->{$attr_name};
    } else {
        return undef;
    }
}
[download]

is much better and easier to read than:

sub getAlpha {
    my $self = shift;

    return $self->{Alpha};
}

sub getBeta {
    my $self = shift;

    return $self->{Beta};
}

sub getGamma {
    my $self = shift;

    return $self->{Gamma};
}
[download]

You have one function that does everything in a very understandable manner. (For those who complain that generic functions are slower, I wonder why you're using OO Perl...) If you want further generic stuff (in this case, boundary checking and the like), you can use a dispatch table to hand off to handlers in the cases where a generic function doesn't encapsulate enough. Or, you could just do your checking outside, either in main code or in another function. The basic idea is that there is one function, at the heart, that does one thing.

Now, I'm contradicting myself, and I know this. But, as the other posters have made clear, there is no hard-and-fast rule as to when a sub is good or not. It very quickly becomes a religious debate. You have to come to your own conclusions. I know my level, and I suspect many of the monks know their own levels, too. Where's yours? That's a matter of experience, which comes only from trial and error.

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