If you only need a list of core en language files, I think you can use the following shell script to obtain it.
#!/bin/sh
MDLHOME=/var/www/html/moodle
cd $MDLHOME
DIRLIST=`find -depth -type d -iname "en"|sed 's/\.\///g'`
for dirname in $DIRLIST
do
ls $dirname/*
done
If you need a copy of all core en language directories and files, you can use the following shell script.
#!/bin/sh
MDLHOME=/var/www/html/moodle
LANGWORK=/home/lang_work
cd $MDLHOME
DIRLIST=`find -depth -type d -iname "en"|sed 's/\.\///g'`
cd $LANGWORK
for dirname in $DIRLIST
do
mkdir -p $dirname
\cp -frp $MDLHOME/$dirname/* ./$dirname/
done