open DATA, "</home/file.conf";

while (<DATA>)
{
        if(m/\END\b/)
        {
                print "$.\n";
                print "$_\n";
                $pos = $.;
                $pos--;
                chomp $pos;
                $DESIRED_LINE_NUMBER = $pos;

        }
}

#$. = 0;
do { $LINE = <DATA> } until $. == $DESIRED_LINE_NUMBER || eof;
print $LINE;


##</code><code>##


Result:

1675 ---> Line found matching Search
# *** END NEW MAPPING RULES SECTION *** ---Txt from Line

    -->Blank Line where I need to add values.