Why isn't this simple method to join elements of 2 arrays not working

Axlex has asked for the wisdom of the Perl Monks concerning the following question:

Hello wise Monks; i am trying to concatenate the lines of 2 files and came up with this simple code

my (@In, $In, @Out, $Out, $InFile, $OutFile);                         
+       # declare variables
    open $InFile, "<", "e:/File1.txt";            # open the exported 
+file in read mode
    open $OutFile, ">>", "e:/File2";
    @In = <$InFile>;
    @Out = <$OutFile>;
    close $InFile;
    close $OutFile;
    for my $k ( 0 .. $#In ) {
        $Out[$k] = "$Out[$k],$In[$k]";
}
    open $OutFile, ">", "e:/File2.txt";            # open the outfile,
+ deleting all content (writemode)
    print $OutFile @Out;
    close $OutFile;
[download]

but i am getting the error: "Use of uninitialized value within @Out in concatenation(.) or string at join.pl"

I know, my programming skills are bad but please, i dont know any other way.

Comment on Why isn't this simple method to join elements of 2 arrays not working Download Code

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Re: Why isn't this simple method to join elements of 2 arrays not working by ikegami (Patriarch) on Sep 21, 2014 at 14:42 UTC
You are trying to read from a file you opened for writing.	[reply]
Re: Why isn't this simple method to join elements of 2 arrays not working by LanX (Saint) on Sep 21, 2014 at 14:44 UTC
`open $OutFile, ">>", "e:/File2";` Is wrong, use `"<"` to read, `@Out` must be empty otherwise. `">>"` means appending ! Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :)}	[reply] [d/l] [select]
Re: Why isn't this simple method to join elements of 2 arrays not working by davido (Cardinal) on Sep 21, 2014 at 18:12 UTC
Just for fun... `use strict; use warnings; use autodie; use Getopt::Long; use File::Slurp qw( read_file write_file ); use List::MoreUtils 'pairwise'; use constant { EMPTY => q{}, FILE1 => 'e:/File1.txt', FILE2 => 'e:/File2.txt' }; my $LIVE = EMPTY; GetOptions('live' => \$LIVE); write_file $LIVE ? FILE2 : \*STDOUT, pairwise { join( ',', map{$_//EMPTY} $a,$b ) . "\n"; } @{slurp(FILE1)}, @{slurp(FILE2)}; sub slurp { read_file shift, array_ref=> 1, chomp => 1 }` [download] By default this will dump its output to STDOUT. Once you're certain it will do what you want, run it with the `--live` flag, and it will overwrite FILE2, which seems to be what you want. I'd probably use copies of the original files until I'm certain. Updated: Handle command-line option via Getopt::Long rather than @ARGV. Dave	[reply] [d/l] [select]