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for (@file1) {
    $h{join ' ',(split / /)[0..3]} = $c++;
}

while (<DATA>) {
    $key = join ' ',(split / /)[0..3];
...
         print if $_ ne $file1[$h{$key}];
    }
}

use strict;
use warnings;
...
A C B D E F H
D B C A I F G
B B C D E F G