Hanging indent in expex preamble

Question

expex has a great way of displaying long glossed lines with a hanging indent by defining \glhangindent globall via lingset. I would like to achieve this also for preamble (\glpreamble) and free translation (\glft)?

I have tried setting \lingset{everyglpreamble=\hangindent=1em,everyglft=\hangindent=1em} but this gives an error (outcommented below).

Alternatively I tried placing \hangindent=1em directly before each line, which works for \glft but not for \glpreamble (setting it for glpreamble results not in hanging indent but the entire line is indented).
Any way how to make this work and set it globally? Help much appreciated!

\documentclass{article}
\usepackage{expex}
%\lingset{everyglpreamble=\hangindent=1em,everyglft=\hangindent=1em}
\begin{document}
\ex \begingl
\glpreamble \hangindent=1em This is a very long sentence to be glossed and I would like the preamble also to have a hanging indent.//
\gla Gloss this//
\glb gl gl//
\glft \hangindent=1em This is a translation of a very long sentence to be glossed and I would like the free translation also to have a hanging indent.//
\endgl \xe
\end{document}

Just for clarification by hanging indent I mean:

This is a very long sentence to be glossed and I would 
        like it to have a hanging indent

Answer 1

Brace the values:

\documentclass{article}
\usepackage{expex}
\lingset{everyglpreamble={\hangindent=1em \hspace*{-\hangindent}},everyglft={\hangindent=1em }}
\begin{document}
\ex \begingl
\glpreamble This is a very long sentence to be glossed and I would like
            the preamble also to have a hanging indent.//
\gla Gloss this//
\glb gl gl//
\glft This is a translation of a very long sentence to be glossed and
      I would like the free translation also to have a hanging indent.//
\endgl \xe
\end{document}