# basic cases
a=1
a+=4
echo $a
x=(1 2 3)
x+=(4 5 6)
echo ${x[@]}
x[4]+=1
echo ${x[@]}
# trickier cases
a+=5 printenv a
echo $a
# if the integer flag is set, ksh93 appears to do arithmetic += and evaluate
# old value as an arithmetic expression
a=
typeset -i a
a+=7
echo $a
b=4+1
typeset -i b
b+=37
echo $b
unset x
x=(1 2 3 4 5)
typeset -i x
x[4]+=7
echo ${x[@]}
unset x
typeset -i x
x=([0]=7+11)
echo ${x[@]}
unset x
x=(1 2 3 4 5)
typeset -i x
#x[4]=7+11
x=(1 2 3 4 [4]=7+11 )
echo ${x[@]}
x=( 1 2 [2]+=7 4 5 )
echo ${x[@]}
x+=( [3]+=9 [5]=9 )
echo ${x[@]}
unset a
a=1
export a+=4
printenv a
printenv a+
unset x
typeset -i x=4+5
echo $x
unset x
typeset x+=4
echo $x
typeset -i x+=5
echo $x
readonly x+=7
echo $x
x+=5