Queries w/ "computed" table names? (eval in Pg?)

["Kynn Jones" <kynnjo@xxxxxxxxx>]

Hi.  Suppose I have a database that contains a "meta table" that holds the names of other the tables in the database, keyed by human-readable but longish strings.  I would like to write queries that first "compute" the names of some tables (i.e. by looking them up in "meta table"), and after that they execute subqueries using these computed table names.  The following invalid SQL illustrates the kind of maneuver I'd like to do:

SELECT x, y, z

  FROM [ SELECT table_name FROM meta_table

          WHERE human_readable_key =

          'some veeeery long and unwieldy string' ];

The stuff in [ brackets ] is not meant to be valid SQL, but rather to suggest that the name of the table for the "outer" query corresponds to the string returned by the "inner" (bracketed) query.

Some programming languages allow the run-time evaluation of a string representing some code in the language.  One way to do what I'd like to do is based on this idea: I would construct the source code for the desired subquery as a string (including the name of the table obtained at run-time from meta_table), and "somehow" evaluate this string.  This "somehow" is what I'm missing.  Is there a way in PostgreSQL to evaluate a string as SQL?

TIA!

kynn