I finally solved it :) Thank you all, great community!

here's my solution:

#! usr/bin/perl

use strict;
use warnings;
use IO::File;

my @out;
my @file_names = ("output1.txt", "output2.txt", "output3.txt");
my $i = 0;
my $file;

if ($#ARGV < 1){
    die "Usage: $0 Argument1 Argument2 ... \n";
}
foreach $file (@ARGV){
    open (READ, $file) || die "Cannot open $file: $!.\n";
    $out[$i] = IO::File->new( ">$file_names[$i]" ) || die "Cannot open
+ $file_names[$i]: $!.\n";

    while (my $line = <READ> ){
        print {$out[$i]} "$line";
    }
    $i++;
}
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