#!/usr/bin/perl
use warnings;
use strict;

# First set up the sample files
my @fileContents = ('a 1 b 2 c 3', 'a 5 d 3', 'a 1 x 4');

@ARGV = ();

for (my $fileNum = 1; @fileContents; ++$fileNum) {
    my $fileName = "file$fileNum.txt";

    open my $fileOut, '>', $fileName or die "Failed to create $fileName: $!\n";
    push @ARGV, $fileName;
    print {$fileOut} shift @fileContents;
}

# Now for the "real" code
my %data;
my $maxFile = @ARGV - 1;

while (<>) {
    my %newData = split;

    $data{$_}[$maxFile - @ARGV] = $newData{$_} for keys %newData;
}

for my $key (sort keys %data) {
    $data{$key}[$maxFile] ||= 0;
    $_ ||= 0 for @{$data{$key}};
    print "$key @{$data{$key}}\n";
}