Perl opening file handle in append mode to read - perl

Question

I have a text file where I have to read the content and append to it. i.e. make a copy of the file and append to it. I wrote the following code
#!/usr/bin/perl
use strict;
use warnings;
my $line;
open FILL, ">> fred"
or warn "Cannot open : $!";
while(<FILL>){
# s/^Author:.*/Author: Randal L. Schwartz/;
# s/^Phone:.*\n//;
# s/^Date:.*/Date: $date/;
$line.=$_;
print $line;
}
select FILL;
print $line;
But it doesn't enter the while loop at all and when I open a filehandle for the same file in read mode and select the file handle in append mode to print it works.
Input :
Program name: granite
Author: Gilbert Bates
Company: RockSoft
Department: R&D
Phone: [phone]
Date: Tues March 9, 2004
Version: 2.1
Size: 21k
Status: Final beta
Output :
Program name: granite
Author: Gilbert Bates
Company: RockSoft
Department: R&D
Phone: [phone]
Date: Tues March 9, 2004
Version: 2.1
Size: 21k
Status: Final beta
Program name: granite
Author: Gilbert Bates
Company: RockSoft
Department: R&D
Phone: [phone]
Date: Tues March 9, 2004
Version: 2.1
Size: 21k
Status: Final beta
This program works correctly
#!/usr/bin/perl
use strict;
use warnings;
my $line;
open FIL, "fred"
or warn "Cannot open : $!";
open FILL, ">> fred"
or warn "Cannot open : $!";
while(<FIL>){
# s/^Author:.*/Author: Randal L. Schwartz/;
# s/^Phone:.*\n//;
# s/^Date:.*/Date: $date/;
$line.=$_;
print $line;
}
select FILL;
print $line;
It appends correctly in file but the terminal output is
Program name: granite
Program name: granite
Author: Gilbert Bates
Program name: granite
Author: Gilbert Bates
Company: RockSoft
Program name: granite
Author: Gilbert Bates
Company: RockSoft
Department: R&D
Program name: granite
Author: Gilbert Bates
Company: RockSoft
Department: R&D
Phone: [phone]
Program name: granite
Author: Gilbert Bates
Company: RockSoft
Department: R&D
Phone: [phone]
Date: Tues March 9, 2004
Program name: granite
Author: Gilbert Bates
Company: RockSoft
Department: R&D
Phone: [phone]
Date: Tues March 9, 2004
Version: 2.1
Program name: granite
Author: Gilbert Bates
Company: RockSoft
Department: R&D
Phone: [phone]
Date: Tues March 9, 2004
Version: 2.1
Size: 21k
Program name: granite
Author: Gilbert Bates
Company: RockSoft
Department: R&D
Phone: [phone]
Date: Tues March 9, 2004
Version: 2.1
Size: 21k
Status: Final beta
Program name: granite
Author: Gilbert Bates
Company: RockSoft
Department: R&D
Phone: [phone]
Date: Tues March 9, 2004
Version: 2.1
Size: 21k
Status: Final beta
Why does it print so many times?

Answer 1

$line is the variable in which you accumulate everything read so far. So within the loop, you probably wanted to do
print $_;
or just
print;
instead of
print $line;
To answer your original question... You will want to open the file in both read and write (append) mode.
open FILL, '>>+', 'fred';
(Please don't use the 2-argument version of open. It's unsafe.)
But this places the file pointer at the end of the file, so you'll have to do a
seek FILL, 0, 0;
before reading. Since you read before writing, it makes no difference whether or not you open the file in append mode.
You should even be able to add another seek after reading the file, but I am not sure whether this is going to be portable across Unix and Windows.