#!perl

use 5.10.0;
use strict;
use warnings;

my %merged = ();
my $index = 0;

map {
    open my $file, '<', $_ or die $!;

    map {
        $merged{$_->[0]} //= [ qw{null} x 3 ];
        $merged{$_->[0]}[$index] = $_->[1];
    }
    map {
        [ m{ \A ( \S+ \s \S+ \s \S+ \s \S+ ) \s ( \S+ ) \z }msx ]
    }
    map {
        chomp; $_
    } (<$file>);

    close $file;

    ++$index;
} qw{gravity magnetics bathymetry};

say join(' ', $_, @{$merged{$_}}) for sort keys %merged;