Question

I want to read and write to an existing file using perl.

can any one tell me what is the mode that i have to use for such purpose:
I am quite confused by the below modes available.
I tried with +> but its not writing to the file.

mode operand create truncate 
read     <   
write    >    ✓      ✓ 
append  >>    ✓  

mode       operand create truncate 
read/write  +<   
read/write  +>       ✓      ✓ 
read/append +>>      ✓  

For eg:
i have a file like below:

one
two 
four

i want to insert a line in between like :

one
two
three
four

Answer 1

Take a look at what perlopentut has to say about Mixing Reads and Writes. The conclusion is that none of the mixed-mode open modes are ideal, and the in-place edit mode (using $^I) is a better solution.

For this particular problem I recommend the Tie::File module, which allows you to treat the file as a simple array.

As an example, to insert the line three into your example data, write

use strict;
use warnings;

use Tie::File;

tie my @file, 'Tie::File', 'myfile.txt' or die $!;

splice @file, 2, 0, 'three';

untie @file or die $!;