[OpenSIPS-Users] define variable problem

[chamo]

hello i have silly question

where could be problem here with this variable
$var(a) = $fU + "@" + $fd;   #without ; is result same
modparam("acc", "radius_extra", "User-Name=$var(a);
Called-Station-Id=$tu; Calling-Station-Id=$fu;
Sip-Translated-Request-URI=$ru")

i am getting errors

Nov 14 13:27:12 [14080] CRITICAL:core:yyerror: parse error in config
file, line 165, column 7-14: syntax error
Nov 14 13:27:12 [14080] CRITICAL:core:yyerror: parse error in config
file, line 165, column 15-16: unknown config variable
Nov 14 13:27:12 [14080] CRITICAL:core:yyerror: parse error in config
file, line 167, column 1-9:

thank you

Regards

Chamo