Merging lines in a file

[Jan Eden]

Hi,

I had the following task: Open a file, read it and merge all pairs of lines containing 
a certain number of tabs. Example:

Blablabla
abc cab bca
123 453 756
Blablabla
Blablabla

Here, lines 2 and three should be merged, while the other lines should remain 
untouched. Expected result:

Blablabla
abc 123
cab 453
bca 756
Blablabla
Blablabla

While I managed to get this done, I doubt that I found a good (fast) solution. So 
before I move on to the large files which have to be processed, I'd like to get your 
input for a better solution.

This is how I did it:

#!/usr/bin/perl -w

use strict;

my (@merge_one, @merge_two, @merge_three);

open (FILE, "file.txt") or die "Cannot open the input file";

my @input_file = <FILE>;

foreach (0..$#input_file) {
    chomp $input_file[$_];
    my $next = $_+ 1;
    chomp $input_file[$next] if $input_file[$next];
    if ($input_file[$_] =~ m/\t/ && $input_file[$next] =~ m/\t/) {
        @merge_one = split /\t/, $input_file[$_];
        @merge_two = split /\t/, $input_file[$next];
        for (0..$#merge_two) {
            $merge_three[$_] = $merge_two[$_] . " " . $merge_one[$_];
        }
        $input_file[$_] = join "\n", @merge_three;
        print $input_file[$_], "\n\n";
        $input_file[$next] = '';
        (@merge_one, @merge_two, @merge_three) = ();
    }
}

my $output = join "\n", @input_file;

open (OUTFILE, ">input_file2.txt");
print OUTFILE $output;


Grateful for any suggestion,

Jan
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