I was wonder if anyone has found it valuable to distinguish between compile-time and run-time module dependencies.

Example - in this case the module Fcntl is a compile-time dependency of module Bar: 

  package Bar;
  use Smart::Comments;
  sub blather {
    ### $foo
  }

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However, in this example, LWP::UserAgent is just a run-time dependency of module Foo: 

  package Foo;
  use LWP::UserAgent;

  sub make_agent { LWP::UserAgent->new }

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It could also be written like this: 
  package Foo;
  # NOTE: this module needs LWP::UserAgent loaded in order to work
  sub make_agent { LWP::UserAgent->new }

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It would then be some other code's responsibility to ensure that LWP::UserAgent was loaded before any subs in package Foo were called.

Specifically, a compile-time dependency is a module which needs to be loaded in order for a compile-check to work. A run-time dependency is one that only required to be loaded at run time.

So the question again - has anyone found it useful to formally declare a module's run-time only dependencies - perhaps with a pragma like: 

use runtime LWP::UserAgent;

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In reply to use: distinguishing compile-time vs run-time dependencies by perl5ever

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