Checking if your kit is complete...
Looks good
'LICENSE' is not a known MakeMaker parameter name.
Note (probably harmless): No library found for -lstree
Writing Makefile for Tree::Suffix
cp lib/Tree/Suffix.pm blib/lib/Tree/Suffix.pm
/home/cpanrun/pa-risc1.1/build/5.6.1/bin/perl -I/home/cpanrun/pa-risc1.1/build/5.6.1/lib/5.6.1/PA-RISC1.1-thread-multi -I/home/cpanrun/pa-risc1.1/build/5.6.1/lib/5.6.1 /home/cpanrun/pa-risc1.1/build/5.6.1/lib/5.6.1/ExtUtils/xsubpp  -typemap /home/cpanrun/pa-risc1.1/build/5.6.1/lib/5.6.1/ExtUtils/typemap -typemap typemap Suffix.xs > Suffix.xsc && mv Suffix.xsc Suffix.c
cc -c  -D_POSIX_C_SOURCE=199506L -D_HPUX_SOURCE +DA1.1 +DS2.0a +z -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -Ae -O +Onolimit   -DVERSION=\"0.19\" -DXS_VERSION=\"0.19\" +z -I/home/cpanrun/pa-risc1.1/build/5.6.1/lib/5.6.1/PA-RISC1.1-thread-multi/CORE  Suffix.c
cpp: "Suffix.xs", line 6: error 4036: Can't open include file 'libstree.h'.
make: *** [Suffix.o] Error 1