use strict;
use warnings;

my %A;       # remembers pairing (x,y) as  $A{x}{y} and $A{y}{x}
my @order;   # set output order here or trust auto-generated @order below
             # e.g. @order = qw(eel horse lion mule tiger);

# autovivify interesting pairings
while (<DATA>) {
  warn("Line $.: cannot understand: $_") , next unless /(\w+);(\w+)/;
  my ($row, $col) = ($1,$2);
  $A{$row}{$col}++; # ++ just triggers the autovivification (see: perlref)
  $A{$col}{$row}++; # uncomment line if relationship is not bidirectional
                    #           ... would break gimmick#1
}

# Gimmick #1: auto-generated list-order when list-order was not given
#             assumption: symmetric relationship -> square matrix;
#             combinations never paired are filtered out - bug or feature?
@order = sort keys %A unless @order; # create order unless given above

# Gimmick #2: fixed auto-width for output (min. width: 2+3 ('###'))
my $width  = 2 + (sort { $a <=> $b } ( map { length $_ } (@order, '###' )) )[-1];
my $format = '%-' . $width . 's';  # printf()-format for fixed width columns

# print header
printf($format, $_) for ( " ", @order );
print "\n";

# print matrix A
for my $row (@order) {
  printf($format, $row);

  for my $col (@order) {
    printf($format, exists $A{$row}{$col} ? "1" : "0");
    # Idea for gimmick#3: $format = f( column )
  }
  print "\n";
}

__DATA__
horse;tiger
lion;mule
lion;tiger
horse;mule