It works fine, only a minor glitch

This would be a sample query:
./check_rrd.pl -R rra_file.rrd –ds data_source -w100 -c150 –start -10min –end -5min

The important thing is the –end -5min, if you use now, the last value might be a NAN, then it would always give a CRITICAL (because there are NaN values)