#   This program is free software: you can redistribute it and/or modify
#   it under the terms of the GNU General Public License as published by
#   the Free Software Foundation, either version 3 of the License, or
#   (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#   GNU General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
POSIXLY_CORRECT=1
x=2
x+=5 eval printf '"$x "'
echo "$x"

unset x
typeset -i x=2
x+=5 eval printf '"$x "'
echo "$x"

a=1
a+=4
echo $a

# idiotically, ksh93 makes these two cases differ (?)
a+=5 printenv a
a+=5 eval printf '"$a "'
echo $a