Re. My Library Is Not Loading!, a pretty useful trick to find what files are missing is to extend your path env var with an empty directory and then grep strace output for its occurrences, e.g.

  mkdir /tmp/empty
  LD_LIBRARY_PATH+=:/tmp/empty  # or PATH, or PERL5LIB, etc.
  strace -f program |& grep /tmp/empty

I had a need to track what files are used by what processes spawned by a program (to infer dependencies between the processes), and it seemed (and probably was) simpler to use ptrace directly rather than to parse strace output, so I wrote https://github.com/orivej/fptrace/ . Soon it turned out useful to dump its data into shell scripts that reflect the tree of spawned processes and let you rerun an arbitrary subtree. I mostly use it to debug build systems, for example to trace configure and examine what env var affected a certain check in a strange way, or to trace make and rerun the C compiler with -dD -E to inspect an unexpected interference between includes.