Suppose that I have two subroutines, each of which has nested if/else conditions, which are identical in all respects except that, deep inside the if/else nest, one sub performs an action in all circumstances, while the other performs an action only if some condition X is true. The action may be called at a number of points within the subroutine depending on the value of arguments.

I would like to be able to refactor out all the code shared by the two subs but am wondering what the best way to handle the differences. Some pseudo-code:

sub alpha {
    my $self = shift;
    ...
    foreach ...
        if ...
            if ...
                if ...
                    push @foo, [ @bar ];
                }
            }
        } else {
            push @foo, [ @bar ];
        }
    }
    push @foo, [ @bar ];
    return \@foo;
}

sub beta {
    my $self = shift;
    ...
    foreach ...
        if ...
            if ...
                if ...
                    push @foo, [ @bar ] if $self->{baz} eq $gamma;
                }
            }
        } else {
            push @foo, [ @bar ] if $self->{baz} eq $gamma;
        }
    }
    push @foo, [ @bar ] if $self->{baz} eq $gamma;
    return \@foo;
}
[download]

Except for the difference between

    push @foo, [ @bar ];
[download]

and

    push @foo, [ @bar ] if $self->{baz} eq $gamma;
[download]

... the two subroutines are identical. Which implies that I could and should refactor out the common code into an internal subroutine. I would like to have a structure like this:

sub alpha {
    my $self = shift;
    my $coderef = sub {1};
    return $self->_internal_sub($coderef);
}

sub beta {
    my $self = shift;
    my $coderef = sub {$self->{baz} eq $gamma};
    return $self->_internal_sub($coderef);
}

sub _internal_sub {
    my $self = shift;
    my $coderef = shift;
    ...
    foreach ...
        if ...
            if ...
                if ...
                    push @foo, [ @bar ] if &$coderef;
                }
            }
        } else {
            push @foo, [ @bar ] if &$coderef;
        }
    }
    push @foo, [ @bar ] if &$coderef;
    return \@foo;
}
[download]

... but of course the values of $self-baz and $gamma are unknown at the time of assignment to $coderef in beta().

I have a feeling I'm missing something obvious here. Can any of the monks suggest a remedy? Thanks.

Jim Keenan

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