I agree with the valid points that were already rasied:

1. use File::Spec (or, I might add, File::Basename) to do this - don't reinvent the wheel.
2. just re-organize the code, put the shared code (i.e. the reg-exp, in this case) in a subroutine, and call that from two different routines

However, my curiosity was piqued about how to go about this, if the need did come up somehow, even though I think solution #2 would be the simplest/best answer most (all?) of the time...

So I came up with this snippet using closures, as you mentioned

for my $wheel (qw/basename dirname/)
{
    no strict 'refs';

    *$wheel = sub
    {
        my ($dir) = shift;

        my ($path, $name) = ($dir =~ m{(.*)/([^/]*)$});

        if ($wheel eq 'basename')
        {
            return $name;
        }
        else
        {
            return $path;
        }
    };
}

my $path = dirname('/tmp/foo/bar');
my $name = basename('/tmp/foo/bar');
print "$path/$name\n";
[download]

Works for me...

Update: Expunged the OPs leaning toothpicks, since I am attributing the snippet to myself ;-)

Update: Or this:

for my $funcname (qw/basename dirname/)
{
    no strict 'refs';

    *$funcname = sub
    {
        my ($dir) = shift;

        my ($path, $name) = ($dir =~ m{(.*)/([^/]*)$});

        if ($funcname eq 'basename')
        {
            return $name;
        }
        else
        {
            return $path;
        }
    };
}

my $path = dirname('/tmp/foo/bar');
my $name = basename('/tmp/foo/bar');
print "$path/$name\n";
[download]