求此脚本完成的功能是什么？

#! /bin/bash
COUNTER=100
echo "Change the counter value currently set at ${COUNTER} ?   [y/n]"
read ANS
if [ "${ANS}" = "y" ] || [ "${ANS}" = "Y" ];then
    echo -n " Enter a sensible value: "
    read VALUE
    expr ${VALUE} + 10 > /dev/null 2>&1
    STATUS=$?
    if [ "${VALUE}" = "" ];then
       echo "you   enterd nothing   " >&2
       exit 1
    elif [ "${STATUS}" != "0" ];then
       echo "you enter a non-numeric " >&2
       exit 1
    else
        COUNTER=$(expr ${COUNTER} + ${VALUE})
        echo " Counter now set to ${COUNTER} "
        exit 0
    fi
fi
echo "do nothing! "
exit 0