I'm not really clear on what you're asking for with extracting /great and putting it back. Both the inital and resulting $a's in your question look the same to me.

Here's what I came up with...

my $a = '/export/home/test/great';
$a =~ / (.*) (\/[^\/]*) /x;
my $front = $1;
my $back = $2;

print "a: $a\n";
print "front: $front\n";
print "back: $back\n";
[download]

Note: I'm using /x to add some whitespace to the regex for clarity. You can ignore the spaces.

That returns...

a: /export/home/test/great
front: /export/home/test
back: /great
[download]

I think the other solutions are affected by regex greed. So they'll pull out the longest string starting with a slash. If I'm oversimplifying things, then I'm sorry.

I hope this helps.