There are 2 main unemployment payments, Jobseekers Benefit and Jobseekers Allowance.
Jobseekers Benefit is based on your PRSI stamps. As well as needing a total number of contributions (at least 2 year's worth) you also need contributions in the relevant year, which is 2 years prior to the claim. Claims made in 2011 rely primarily on 2009 contributions and those made from January next year will rely on 2010 contributions.
As you've been out of the country for so long you won't have sufficient stamps to claim Jobseekers Benefit based on your Irish contributions.
If you have been working in another EU country, then you can combine your social insurance record from the country where you were working, but to do this you must have worked at least one week since last returning to Ireland. If you haven't worked in Ireland since your return, you won't be able to rely on your EU contributions, although there is an exception if you have returned to Ireland for family reasons.
There are also bilateral agreements with a small number of other countries outside of the EU, which allow you to rely on contributions made there to count here.
All the above relates to Jobseekers Benefit.
If you do not qualify for Jobseekers Benefit, you may qualify for Jobseekers Allowance. This depends on habitual residence. The Jobseekers Benefit/PRSI based payment does not require habitual residence.
See the following links for more detail:
JObseekers Benefit - http://www.welfare.ie/EN/Schemes/JobseekerSupports/JobseekersBenefit/Pages/jb.aspx
Jobseekers Allowance -
http://www.welfare.ie/EN/Schemes/JobseekerSupports/JobseekersAllowance/Pages/ja.aspx
Habitual Residence -
http://www.welfare.ie/EN/OperationalGuidelines/Pages/habres.aspx
Useful examples of how habitual residence is supposed to be determined -
http://www.welfare.ie/EN/OperationalGuidelines/Pages/habres_supplement.aspx