-- test.lua
s = "\\sitem  Hello\n\\end{itemize}"
print(s)

result = string.gsub ( s, '\\sitem%s+(.-)(\n\\)' , '\\item\\makefirstuc {%1},%2')
print("\nAfter gsub")
print(result)

--After gsub
--\item\makefirstuc {Hello},
--\end{itemize}