TPL: pass a parameter to a perl function from iw_value

VijayBabu

I have a perl function with declaration as below...
[html]

sub getEEQName
{
$id = shift;
.
.
}

[/html]
How to call this perl function and pass a parameter (which will be from a dcr field) from inside the iw_value tag?
I tried to pass a constant like [html] <li> <iw_value name='(getEEQName(648))'/> </li> [/html]and it is working
but the below code is not working...
[html] <li> <iw_value name='(getEEQName(dcr.existing_id))'/> </li> [/html]

Please help.