There is a way to do this with the perl-api (core). You can use the get_species_and_object_type method in the registry, and you do not have to know the species. This will work with any Ensembl stable ID (ENSORLP00000023599 would work).

Here's the code:

my $stable_id = 'ENST00000326632';
my ( $species, $object_type, $db_type ) =
  $registry->;get_species_and_object_type($stable_id);
my $adaptor =
  $registry->get_adaptor( $species, $db_type, $object_type );
my $object = $adaptor->fetch_by_stable_id($stable_id);

After this, go in with the object and get the display label for the associated gene name.

Perl docs are here.

A tutorial, if you need it, is here

Don't forget, any queries like this can go directly to us (helpdesk@ensembl.org)

As far as I can see, there is no web service around that can do exactly what you want. If you know the species of interest, you could quite easily retrieve it from BioMart using a simple XML formatted query:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE Query>
<Query  virtualSchemaName = "default" formatter = "TSV" header = "0" uniqueRows = "0" count = "" datasetConfigVersion = "0.6" >

    <Dataset name = "olatipes_gene_ensembl" interface = "default" >
        <Filter name = "ensembl_peptide_id" value = "ENSORLP00000023599"/>
        <Attribute name = "external_gene_id" />
        <Attribute name = "ensembl_peptide_id" />
    </Dataset>
</Query>

You can send this query to their web service using a simple GET request if you like:

http://www.biomart.org/biomart/martservice?query=<Query virtualSchemaName="default" formatter="TSV" header="0" uniqueRows="0" count="" datasetConfigVersion="0.6"><Dataset name="olatipes_gene_ensembl" interface="default"><Filter name="ensembl_peptide_id" value="ENSORLP00000023599"/><Attribute name="external_gene_id"/><Attribute name="ensembl_peptide_id"/></Dataset></Query>

One solution is thus that you make a simple lookup table where based on the letters before the numbers (in this case ENSORLP) you find out which data set in BioMart to query. This is obviously a pain since you would have to keep it up-to-date with new versions of Ensembl.

The other way to go about it is to grudgingly accept that the web services cannot do what the web interface can, and thus to make your script access the web interface. Yes it is ugly, but it gets the job done.

In your example, you can perform the web interface query by requesting this URL.

In the resulting HTML, you should identify a section like this:

<table class="search_results"> 
<tr><th colspan="2">By Feature type</th></tr> 
<tr><td><a href="/Multi/Search/Details?species=all;idx=;q=ENSORLP00000023599">Total</a></td><td><a href="/Multi/Search/Details?species=all;idx=;q=ENSORLP00000023599">1</a></td></tr> 
      <tr> 
<td><a href="/Multi/Search/Details?_C=eJyLz2FIzWOIL8tjSElNSyzNKWGIL2Rw9Qv2D*IJMAADI2NTS0uF5PyigvyixJJU*ZKi1FQrpZD8Av3g*NKi5FT9VDMDJYb4jMwSt9KcHAZDAwYARHIZlw__&_c=%2b15927579347680844937" class="collapsible"><img src="/i/list_shut.gif" alt="&gt;" style="padding-right:4px" />Gene</a> 
<ul class="shut"> 
<li><a href="/Multi/Search/Details?_C=eJyLz2FIzWOIL8tjSElNSyzNKWGIL2Rw9Qv2D*IJMAADI2NTS0uF5PyigvyixJJU*ZKi1FQrpZD8Av3g*NKi5FT9VDMDJYb4jMwSt9KcHAZDAwYARHIZlw__&_c=%2b15927579347680844937&_c=%2b10649513383310789308">Oryzias latipes (1)</a></li></ul> 
</td> 
<td style="width:5em"><a href="/Multi/Search/Details?_C=eJyLz2FIzWOIL8tjSElNSyzNKWGIL2Rw9Qv2D*IJMAADI2NTS0uF5PyigvyixJJU*ZKi1FQrpZD8Av3g*NKi5FT9VDMDJYb4jMwSt9KcHAZDAwYARHIZlw__&_c=%2b15927579347680844937">1</a> 
</tr> 
</table>

From this, you would extract the last URL mentioned:

http://ensembl.org/Multi/Search/Details?_C=eJyLz2FIzWOIL8tjSElNSyzNKWGIL2Rw9Qv2D*IJMAADI2NTS0uF5PyigvyixJJU*ZKi1FQrpZD8Av3g*NKi5FT9VDMDJYb4jMwSt9KcHAZDAwYARHIZlw__&_c=%2b15927579347680844937

Retrieving that page, will yield you some HTML inside which you look for <p>Your query matched 1 entries in the search database</p>, after which you'll find the link to the next page to retrieve:

http://www.ensembl.org/Oryzias_latipes/Gene/Summary?g=ENSORLG00000018912;r=scaffold676:104884-110194;t=ENSORLT00000023600

Inside this HTML file you pull out the part that looks like <h2 class="caption">Gene: HRAS (ENSORLG00000018912)</h2>, which will give you the gene name for your identifier.

This solution is obviously a pain to implement, likely to break if Ensembl makes changes to their web interface, and ugly as sin. In contrast to the first solution, however, it should be able to automatically deal with Ensembl updating their database with more genomes.