#!/usr/bin/env perl -w
use v5.020;
my @F1;
my @recs;
while (my $line = <DATA>) {
    chomp $line;
    my @F = split '&', $line;
    if ($. == 1) {
        @F1 = @F;
    }
    die "NF mismatch" if +@F1 != +@F;
    push @recs, \@F;
    for (my $i = 0; $i < @F; $i++) {
        next unless defined $F1[$i];
        if ($F1[$i] ne $F[$i]) {
            $F1[$i] = undef;
        }        
    }        
}

for my $rec (@recs) {
    my $i = 0;
    for my $field (@$rec) {
        unless (defined $F1[$i++]) {
            print "$field\t";
        }        
    }
    say "";
}



__DATA__
a=1&b=1&c=1&d=2&e=&f=3
a=1&b=2&c=3&d=2&e=&f=4
a=1&b=2&c=5&d=1&e=&f=5