`requires` will try to locate a **NSBundle** at print time. If the bundle
identifier matches, then the bundle will get loaded. The idea is to be able to
load available functionality to a standalone script.

#### Example
{% if __FOUNDATION__ == "Mulle" %}
{% requires "com.mulle-kybernetik.foundation" %}
{% else %}
{% requires "com.apple.Foundation" %}
{% endif %}

requires searches in the following places:

*  first in all already loaded bundles and frameworks
*  in the mainBundle builtInPlugInsPath
*  it then will search through all Library directories Frameworks and PlugIns
*  Turn on the ``MULLESCION_DUMP_BUNDLE_SEARCHPATH`` environment variable to see
the paths searched.

``requires`` should not be used in multi-line statements.