I thought I'd see if I could use ConTeXt. Here is my first try, hello.tex.
\starttext
\input header
Hello, World!\startlua
a = 1.5
b = 1.8
c = a * b
tex.print(c)
\stoplua plus1.
\stoptext
Didn't work because the file header.tex could not be found, even
though kpsewhich can find it.
(hello.tex
publications : loading formatting style from bxml-apa
(/usr/local/libexec/ConTeXt/tex/texmf-context/tex/context/base/bxml-apa.mkiv)
ConTeXt ver: 2010.06.23 12:45 MKIV fmt: 2011.12.24 int: english/english
system : cont-new loaded
(/usr/local/libexec/ConTeXt/tex/texmf-context/tex/context/base/cont-new.tex
systems : beware: some patches loaded from cont-new.tex
(/usr/local/libexec/ConTeXt/tex/texmf-context/tex/context/base/cont-new.mkiv))
system : cont-fil loaded
(/usr/local/libexec/ConTeXt/tex/texmf-context/tex/context/base/cont-fil.tex
loading : ConTeXt File Synonyms
)
system : cont-sys.rme loaded
(/usr/local/libexec/ConTeXt/tex/texmf-context/tex/context/user/cont-sys.rme (/usr/local/libexec/ConTeXt/tex/texmf-context/tex/context/base/type-def.mkiv) (/usr/local/libexec/ConTeXt/tex/texmf-context/tex/context/base/type-lua.mkiv) (/usr/local/libexec/ConTeXt/tex/texmf-context/tex/context/base/type-siz.mkiv) (/usr/local/libexec/ConTeXt/tex/texmf-context/tex/context/base/type-otf.mkiv))
system : hello.top loaded
%
% begin of optionfile
%
% % runtime options files (command line driven)
% \unprotect
% % feedback and basic job control
% % handy for special styles
% \startluacode
% document = document or { }
% document.arguments={
% }
% document.files={
% "hello",
% }
% \stopluacode
% % process info
% \setupsystem[inputfile=hello]
% \setupsystem[\c!n=1,\c!m=1]
% % modes
% % options (not that important)
% \startsetups *runtime:options
% \setupoutput[pdftex]
% \stopsetups
% % styles and modules
% \startsetups *runtime:modules
% \stopsetups
% % done
% \protect \endinput
%
% end of optionfile
%
(hello.top)
fonts : preloading latin modern fonts
{/usr/local/libexec/ConTeXt/tex/texmf/fonts/map/dvips/lm/lm-math.map}{/usr/local/libexec/ConTeXt/tex/texmf/fonts/map/dvips/lm/lm-rm.map}{/usr/local/libexec/ConTeXt/tex/texmf-context/fonts/map/pdftex/context/mkiv-base.map}
bodyfont : 12pt rm is loaded
language : language en is active
systems : begin file hello at line 1
! I can't find file `header'.
l.2 \input header
Please type another input file name:
! Emergency stop.
l.2 \input header
End of file on the terminal!
! ==> Fatal error occurred, no output PDF file produced!