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/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 Suffix.xs > Suffix.xsc && mv Suffix.xsc Suffix.c
gcc -c  -DUSE_REENTRANT_API -D_GNU_SOURCE -D_REENTRANT -fno-strict-aliasing -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -O2   -DVERSION=\"0.19\" -DXS_VERSION=\"0.19\" -fpic -I/home/cpanrun/build/5.6.1/lib/5.6.1/i686-linux-thread-multi/CORE  Suffix.c
Suffix.xs:6: libstree.h: No such file or directory
make: *** [Suffix.o] Error 1