The MVP INI file reader reads INI files, but can handle properties with
multiple values. The identification of properties that may have multiple
entries is done by section, on a plugin basis. For example, given the
following file:

[Foo::Bar]
x = 1
y = 2
y = 3

MVP will, upon reaching this section, load Foo::Bar and call a method (by
default 'multivalue_args') on it, to determine which property names may
have multiple entries. If the return value of that method includes 'y',
then the entry for 'y' in the Foo::Bar section will be an arrayref with two
values. If the list returned by 'multivalue_args' did not contain 'y', then
an exception would be raised while reading this section.