array-1[0] array-2[0]...array-n[0]
array-1[1] array-2[1]...array-n[1]
    .          .     ...    .
    .          .     ...    .
    .          .     ...    .
array-1[n] array-2[n]...array-n[n]

##</code><code>##

array-1 . ' ' . array-2 . ' ' . array-n

##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

$| = 1;

my @timestamp;
my @doc_read;
my @result;
my $write = 'write.txt';
my $line;
my $text;
my $arg;
my $date = localtime();

sub read {

    foreach $arg (@_) {
	open (READ, "<" , $arg)
	    or die ("Could not open: ".$arg." - $!\n");

	while ( @doc_read = <READ> ) {

	    chomp @doc_read;	

	    foreach $line (@doc_read) {
		@result = split (':', $line);
	
		push (@timestamp, $result[3]);

	    }
	}

	close (READ)
	    or die ("Could not close: ".$arg." - $!\n");

    }
  
    return @timestamp;
}

sub write {

    open (WRITE , ">>" , $write )
	or die ("Could not open: ".$write." - $!\n");

    print WRITE  "\n" . $date . "\n";
    
    foreach $_ (@_) {
	print WRITE $_ . "\n";
    }

    close (WRITE)
	or die ("Could not close: ".$write." - $!\n");

    my $text = "Successfully writen on ".$write.".\n";
    
    return ($text);

}

my @values = &read(@ARGV);

print Dumper (\@values);

my $final = &write(@values);

print "\n" . $final . "\n";

##</code><code>##

Line_1:Line_1_1:Line_1_2:Line_1_3:Line_1_4
Line_2:Line_2_1:Line_2_2:Line_2_3:Line_2_4
Line_3:Line_3_1:Line_3_2:Line_3_3:Line_3_4
Line_4:Line_4_1:Line_4_2:Line_4_3:Line_4_4

##</code><code>##

Line_5:Line_5_1:Line_5_2:Line_5_3:Line_5_4
Line_6:Line_6_1:Line_6_2:Line_6_3:Line_6_4
Line_7:Line_7_1:Line_7_2:Line_7_3:Line_7_4
Line_8:Line_8_1:Line_8_2:Line_8_3:Line_8_4

##</code><code>##

$VAR1 = [
          'Line_1_3',
          'Line_2_3',
          'Line_3_3',
          'Line_4_3'
        ];

##</code><code>##

$VAR1 = [
          'Line_1_3',
          'Line_2_3',
          'Line_3_3',
          'Line_4_3',
          'Line_5_3',
          'Line_6_3',
          'Line_7_3',
          'Line_8_3'
        ];

##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper qw(Dumper);
use constant ARGUMENTS => scalar 2;

$| = 1;

my @timestamp_first;
my @timestamp_second;
my $write = 'output.txt';

sub first {
    
    open (FIRST, "<" , $ARGV[0])
	or die ("Could not open: ".$ARGV[0]." - $!\n");

    while ( my @first_read = <FIRST> ) {

	chomp @first_read;	

	foreach $_ (@first_read) {
	    my @result_first = split (':', $_);

	    if (/^\s*$/) { # /^\s*$/ check for "blank" lines may contain spaces or tabs
		next;
	    }

	    push (@timestamp_first, $result_first[3]);

	}
    }

    close (FIRST)
	or die ("Could not close: ".$ARGV[0]." - $!\n");
    
    return @timestamp_first;
}

sub second {
    
    open (SECOND, "<" , $ARGV[1])
	or die ("Could not open: ".$ARGV[1]." - $!\n");

    while ( my @second_read = <SECOND> ) {

	chomp @second_read;

	foreach $_ (@second_read) {
	    my @result_second = split (':', $_);

	    if (/^\s*$/) { # /^\s*$/ check for "blank" lines may contain spaces or tabs
		next;
	    }

	    push (@timestamp_second, $result_second[3]);

	}
    }

    close (SECOND)
	or die ("Could not close: ".$ARGV[1]." - $!\n");
    
    return @timestamp_second;
}

sub write {

    open (WRITE , ">>" , $write )
	or die ("Could not open: ".$write." - $!\n");
    
    foreach $_ (@_) {
	print WRITE $_ . "\n";
    }

    close (WRITE)
	or die ("Could not close: ".$write." - $!\n");

    my $text = "Successfully writen on ".$write.".\n";
    
    return ($text);
}

sub check {
    
    if (@ARGV < ARGUMENTS || @ARGV > ARGUMENTS) {
	die "Please enter ".ARGUMENTS." files to read!\n";
    }

}

&check(@ARGV);
my @first_values = &first($ARGV[0]);
my @second_values = &second($ARGV[1]);

my @final;
my $num = @first_values;

for($_ = 0; $_ < $num; $_++) {
    push (@final , $first_values[$_] . ' ' . $second_values[$_]);
}

print Dumper (\@final);

my $date = time();

my $output = &write(@final);

print "\nResult: ".$output."";

##</code><code>##

$VAR1 = [
          'Line_1_3 Line_5_3',
          'Line_2_3 Line_6_3',
          'Line_3_3 Line_7_3',
          'Line_4_3 Line_8_3'
        ];

Result: Successfully writen on output.txt.