That's a first step in the right direction. Now, you don't want to print the line number of the previous line, but the content of the previous line. So you will need to come up with some way to remember the previous line and output it when the current line matches /^END$/ (I note you wrote /\END\b/, but I assume that's not what you mean). As I outlined several replies before this one, one possible approach could be:

1. Check the current line
2. If it matches /END/, print the previous line (as remembered)
3. Remember the current line as "previous line" in a variable

This is ghetto, but it works... since I now know the line where I need to edit, how would I then edit the file and input data at that specific line?

#!/usr/bin/perl

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;
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Have you actually tested your code? Assigning to $. does not reset the file pointer in any way. You need to either use seek, or go a step back and look at the original suggestion of using Tie::File. Or, actually, start thinking about the approach I outlined twice already.