Unix shell: Environment variable works for file system but not for ASM path

Question

We would like to switch from file system to ASM for data files of Oracle tablespaces. For the path of the data files, we have so far used environment variables, e.g.,
CREATE TABLESPACE BMA DATAFILE '${ORACLE_DB_DATA}/bma.dbf' SIZE 2M AUTOEXTEND ON;
This works just fine (from shell scripts, PL/SQL packages, etc.) if ORACLE_DB_DATA denotes a file system path, such as "/home/oracle", but doesn’t work if the environment variable denotes an ASM path like "\+DATA/rac/datafile". I assume that it has something to do with "+" being a special character in the shell. However, escaping "\+" didn’t work. I tried with both bash and ksh.
Oracle managed files (e.g., set DB_CREATE_FILE_DEST to +DATA/rac/datafile) would be an option. However, this would require changing quite a few scripts and programs. Therefore, I am looking for a solution with the environment variable. Any suggestions?
The example below is on a RAC Attack system (http://en.wikibooks.org/wiki/RAC_Attack_-OracleCluster_Database_at_Home). I get the same issues on Solaris/AIX/HP-UX on 11.2.0.3 also.
Thanks,
Martin
==== WORKS JUST FINE WITH ORACLE_DB_DATA DENOTING FILE SYSTEM PATH ====
collabn1:/home/oracle[RAC1]$ export ORACLE_DB_DATA=/home/oracle
collabn1:/home/oracle[RAC1]$ sqlplus "/ as sysdba"
SQL*Plus: Release 11.2.0.1.0 Production on Fri Aug 24 20:57:09 2012
Copyright (c) 1982, 2009, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,
Data Mining and Real Application Testing options
SQL> CREATE TABLESPACE BMA DATAFILE '${ORACLE_DB_DATA}/bma.dbf' SIZE 2M AUTOEXTEND ON;
Tablespace created.
SQL> !ls -l ${ORACLE_DB_DATA}/bma.dbf
-rw-r----- 1 oracle asmadmin 2105344 Aug 24 20:57 /home/oracle/bma.dbf
SQL> drop tablespace bma including contents and datafiles;
==== DOESN’T WORK WITH ORACLE_DB_DATA DENOTING ASM PATH ====
collabn1:/home/oracle[RAC1]$ export ORACLE_DB_DATA="+DATA/rac/datafile"
collabn1:/home/oracle[RAC1]$ sqlplus "/ as sysdba"
SQL*Plus: Release 11.2.0.1.0 Production on Fri Aug 24 21:08:47 2012
Copyright (c) 1982, 2009, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,
Data Mining and Real Application Testing options
SQL> CREATE TABLESPACE BMA DATAFILE '${ORACLE_DB_DATA}/bma.dbf' SIZE 2M AUTOEXTEND ON;
CREATE TABLESPACE BMA DATAFILE '${ORACLE_DB_DATA}/bma.dbf' SIZE 2M AUTOEXTEND ON
ERROR at line 1:
ORA-01119: error in creating database file '${ORACLE_DB_DATA}/bma.dbf'
ORA-27040: file create error, unable to create file
Linux Error: 2: No such file or directory
SQL> -- works if I substitute manually
SQL> CREATE TABLESPACE BMA DATAFILE '+DATA/rac/datafile/bma.dbf' SIZE 2M AUTOEXTEND ON;
Tablespace created.
SQL> drop tablespace bma including contents and datafiles;

Answer 1

My revised understanding is that it is not a shell issue with replacing +, but an Oracle problem. It appears that Oracle first checks whether the path starts with a "+" or not. If it does not (file system), it performs the normal environment variable resolution. If it does start with a "+" (ASM case), Oracle does not perform environment variable resolution. Escaping, such as "\+" instead of "+" doesn't work either.
To be more specific regarding my use case: I need the substitution to work from SQL*Plus scripts started with @script, PL/SQL packages with execute immediate, and optionally entered interactively in SQL*Plus.
Thanks,
Martin