apt install libplplot-dev, but I experience the problem reported in issue 6

Yep, sudo apt-get install libplplot-dev worked fine. Thanks !

I don't experience the problem reported in issue 6, perhaps because I'm trying to install version 0.74. The PLplot.so loads without any problem - but there are some test failures (including a segfault):

Test Summary Report
-------------------
t/plplot.t              (Wstat: 139 Tests: 15 Failed: 0)
  Non-zero wait status: 139
  Parse errors: No plan found in TAP output
t/plplot_library_tests.t (Wstat: 1024 Tests: 210 Failed: 4)
  Failed tests:  69, 71, 124-125
  Non-zero exit status: 4
Files=3, Tests=225, 42 wallclock secs ( 0.08 usr  0.01 sys + 18.27 cus
+r  2.41 csys = 20.77 CPU)
Result: FAIL
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As regards t/plplot.t:

$ perl -Mblib t/plplot.t
ok 1 - An object of class 'PDL::Graphics::PLplot' isa 'PDL::Graphics::
+PLplot'
ok 2 - Simple line plot
ok 3 - Simple line plot with LINEWIDTH specified
ok 4 - Symbol plot
ok 5 - Lines and symbols
ok 6 - Sample layer statistics plot
ok 7 - Setting pagesize
ok 8 - Line plot with gaps (plgapline)
ok 9 - Setting JUSTify = 1
ok 10 - Printing text inside and outside of plot window
ok 11 - Colored symbol plot with key
ok 12 - Colored symbol plot with key: reverse rainbow
ok 13 - Colored symbol plot with key, via low level interface
ok 14 - plgvpd call works correctly
ok 15 - plgvpw call works correctly
Segmentation fault (core dumped)
[download]

Not sure how many tests t/plplot.t wants to run (no_plan), but ok() gets called more than 15 times.
At least the module is installable .... and usable, unless you want to utilize any of the features that are failing/segfaulting.

Cheers,
Rob