Add a given path component to a given path variable

pextend.sh

## Add a given path component ($2) to the given path variable ($1).
pextend ()
{
local pvar=$1
local p=$(eval "echo \$$pvar")
local dname=$2
if [ -d $dname ] ; then
   case $p in 
   *${dname}* ) return ;;
   * ) eval "${pvar}=\"${dname}:${p}\"" ;;
   esac 
fi
}