#!/usr/bin/perl -w

use strict;

my %F1;
my @recs;
while (my $line = <DATA>) {
    chomp $line;
    my @F = split '&', $line;
    if ($. == 1) {
        $F1{$_} = 0 for (@F);
    }
    die "NF mismatch" if keys %F1 != @F;
    push @recs, \@F;

    foreach (@F) {
        $F1{$_}++ if exists $F1{$_};
    }
}

for my $rec (@recs) {
    for my $field (@$rec) {
         print "$field\t" unless exists $F1{$field} and $F1{$field} == $.;
    }
   print "\n";
}

__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

##</code><code>##

b=1     c=1     d=2     f=3
b=2     c=3     d=2     f=4
b=2     c=5     d=1     f=5