Perhaps a trick stolen from File::Spec could help you? Have a class defining an OS-independant interface, make that class inherit from OS-specific classes. Make the OS-specific classes inherit from an OS-independant base class, if needed.

Something like this:

Update: Use one file per package (<code> block), don't stuff everything into a single file.

package Foo::Bar;

use strict;
use warnings;

use parent "Foo::Bar::$^O"; # will die here for any OS not yet support
+ed

1;

=pod

Documentation here

=cut
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package Foo::Bar::MSWin32;

use strict;
use warnings;
use parent 'Foo::Bar::base';

use Win32::OLE;

sub frob
{
    Win32::OLE->...
}

# ...

1;
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package Foo::Bar::unixoid;

use strict;
use warnings;
use parent 'Foo::Bar::base';

sub frob
{
    # do it without Win32::OLE
}

# ...

1;
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package Foo::Bar::linux;
use parent 'Foo::Bar::unixoid';
1;
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package Foo::Bar::solaris;
use parent 'Foo::Bar::unixoid';
1;
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package Foo::Bar::cygwin;
use parent 'Foo::Bar::MSWin32'; # assuming you can use OLE with cygwin
+ - never tried it
1;
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package Foo::Bar::base;

use strict;
use warnings;

sub new
{
    my $proto=shift;
    my $class=ref($proto)||$proto;
    my $self=bless {},$class;
    $self->init(@_) or die "init() failed";
    return $self;
}

sub init
{
    # ...
}

sub some_generic_function
{
    # ...
}

1;
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And elsewhere in your code:

use Foo::Bar;

my $f=Foo::Bar->new();
$f->frob('bla','bla');
$f->some_generic_function();
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If you don't like or don't need OOP, add something similar to File::Spec::Functions.

Note that you don't need to inherit from Exporter with any sufficiently modern Perl, even if File::Spec::Functions does. File::Spec is old code, with its own set of problems. It's good, but not perfect. Using File::Spec::Unix as default is ok, but making all other classes inherit from File::Spec::Unix looks strange. And File::Spec also has a design problem.

Alexander