-e option not supported in some gnuplot versions
The darshan-job-summary.pl script relies on sending commands into gnuplot with the -e argument. It also checks that the version of gnuplot is at least 4.2.
However, it appears that gnuplot 4.2 patchlevel 3 (or maybe some particular builds of it) do not support this option. See mailing list thread here, reported by Rene Salmon:
We need to see if we should refine our gnuplot version number check, or if there is some runtime test we should be doing to safely detect/report the problem.