Re: Using perl module if env is enabled

[davido]

Keep in mind that for non-trivial code an optional dependency can cause spaghetti-like code with conditionals peppered throughout the code base:

if(exists $INC{'Example/Module.pm'}) {...}

...or...

if (__PACKAGE__->can('example')) {...}

...or any of a number of other strategies for detecting if the optional module got loaded. This is a situation where it's usually better to encapsulate the optional dependency so that the calling code doesn't have to care whether it was available or not:

package SomeThing;

use Exporter;

BEGIN {
    if (eval "require MyOptional; 1;") {
        MyOptional->import('foo');
    }
    else {
        *foo = sub { # fallback code here. };
    }
}

use parent 'Exporter';
our @EXPORT = qw(foo);

1;

package main;

use SomeThing;

foo();

Now everywhere you wanted foo() you can just call it and not worry about whether or not it got loaded at startup by an external dependency, or by a fallback sub that you created yourself. This is just one of many ways to do it. An encapsulating OO class might work better, or dependency injection into a consuming object could be better; it depends a lot on your use case. But the goal is to reduce the pervasiveness of conditional logic in your code to only the one place.