In case the environment variables in question involve LD_LIBRARY_PATH, and in case you're using Apache, see SetEnv/PassEnv.

LD_LIBRARY_PATH is special in that (on some operating systems like Solaris¹) it needs to be set before the process is started that would need it for dynamic linking (this is because the runtime linker caches the search paths on exec). That means that simply changing the environment from within the script itself may not work.

In case you do want to set it from within the script (as opposed to having the webserver set it, as suggested above), you'll need to re-exec the script after having changed the environment. This has been discussed a few times here, so you should be able to find related sample code.  Update: see PATH is not setting - PERL, for example.

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¹ as you mentioned crle, I figured you might be on Solaris

U are like the Sherlock Holmes in Computer Land man .. Awesome... Anyway, Do you know of any other way by which Dynamic Linking Lib paths can be set, other than LD_LIB_PATH and crle??
Cause among two Solaris boxes, the code executes fine even on the browser, without setting libs using crle..

Regards,
Blub:)

Before trying other things I would try something like:

#!/usr/bin/perl
BEGIN {
    unless ($ENV{DONE_RESTARTING_MYSELF}) {  # avoid endless loop...
        $ENV{DONE_RESTARTING_MYSELF} = 1;
        $ENV{ORACLE_HOME}     = "/opt/oracle/product/10.2.0/client_1";
        $ENV{LD_LIBRARY_PATH} = "/opt/oracle/product/10.2.0/client_1/l
+ib32:/usr/local/lib/sprolib:/usr/local/lib:/usr/lib:/usr/openwin/lib:
+/usr/dt/lib:/usr/lib:/usr/ucblib";

        exec $0, @ARGV;    # <---
    }
}
use DBI;
# ...
[download]

Or simply use a shell wrapper around your Perl script:

#!/bin/sh
export ORACLE_HOME=/opt/oracle/product/10.2.0/client_1
export LD_LIBRARY_PATH=/opt/oracle/product/10.2.0/client_1/lib32:/usr/
+local/lib/sprolib:/usr/local/lib:/usr/lib:/usr/openwin/lib:/usr/dt/li
+b:/usr/lib:/usr/ucblib

/path/to/your/script.pl
[download]

As for the ELFCLASS64 error, the reason is that the (64-bit) lib is being found in /opt/oracle/product/10.2.0/client_1/lib, instead of the 32-bit one in the .../lib32 directory that you tried to specify via LD_LIBRARY_PATH — because setting the env variable too late (after exec of perl) doesn't have any effect, as already mentioned.

Something like $ENV{'ORACLE_HOME'} = $your_oracle_home;?

Update: s/orace/oracle/

Yes, I have set that.. But still no go..

Can you post relevant code please?

Thanks for the ultra quick response dude(ette)..
I am aware of %ENV hash, I am setting $ENV{'LD_LIBRARY_PATH'}=ORACLE_LIB_DIRECTORY.. Even after setting this, i am getting an error.. But this error vanishes once i set the variable using crle..

Is this the only environment variable you set? what's the error? Is there another process on the same machine involved?

Also the DBD::Oracle documentation talks about connecting, environment variables and so on. Did you read it?