A possible way to do so is to pass $error on to log_action a second parameter. That would be:

sub exec{
#...
&log_action('error',$error);
}

sub log_action{
  my $i = shift; #get first parameter
  my $error = shift; get second parameter
# note that this $error here is not the same variable but has the same
+ value!
#do whatever with it...
}
[download]

You should also consult your Camel Book on Subroutines.

Hope this helps,
C-Keen