Yes, I too ran across this. Still line 27. Take out the '.' (period) and it runs just fine and charts generate.
File (default install):
/opt/splunk/etc/apps/unix/bin/interfaces.sh
This occurs on CentOS 6.3:
2.6.32-279.1.1.el6.x86_64 #1 SMP Tue Jul 10 13:47:21 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
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