Checking if your kit is complete...
Looks good
Note (probably harmless): No library found for -lplplotd
Writing Makefile for Graphics::PLPLOT
cp PLPLOT.pm blib/lib/Graphics/PLPLOT.pm
/home/cpanrun/build/5.6.1/bin/perl -I/home/cpanrun/build/5.6.1/lib/5.6.1/i686-linux-thread-multi -I/home/cpanrun/build/5.6.1/lib/5.6.1 /home/cpanrun/build/5.6.1/lib/5.6.1/ExtUtils/xsubpp  -typemap /home/cpanrun/build/5.6.1/lib/5.6.1/ExtUtils/typemap -typemap typemap PLPLOT.xs > PLPLOT.xsc && mv PLPLOT.xsc PLPLOT.c
Please specify prototyping behavior for PLPLOT.xs (see perlxs manual)
gcc -c -I/usr/local/include -DUSE_REENTRANT_API -D_GNU_SOURCE -D_REENTRANT -fno-strict-aliasing -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -O2   -DVERSION=\"0.01\" -DXS_VERSION=\"0.01\" -fpic -I/home/cpanrun/build/5.6.1/lib/5.6.1/i686-linux-thread-multi/CORE  PLPLOT.c
PLPLOT.xs:33: plplot/plplot.h: No such file or directory
make: *** [PLPLOT.o] Error 1