Here is a little script I use which does the same thing as Yogesh suggested. Simply call the script with oldvalue and newvalue -- every file in the directory will be updated so use with care
#!/bin/ksh
case $# in
0) echo "\nUsage: replace oldvalue newvalue\n"
exit 1
;;
*) echo "\n\n oldvalue: $1\t\t newvalue: $2\n\n"
echo "================================================"
echo "BEFORE"
echo "================================================"
grep $1 *
perl -pi -e "s/$1/$2/g" *
echo "================================================"
echo "AFTER"
echo "================================================"
grep $2 *
esac