sub ikegami1 {
    my ($ref, @wordsCopy) = @words;

    while, ($ref =~ /(.)/g) {
       my $letter = $1; 
       my $pos = $-[0]; 
       for ( @wordsCopy ) 
       { 
           if ( substr( $_, $pos, 1 ) ne $letter )
           { 
               substr( $ref, $pos, 1, '-' );
               last;
           } 
       }
    }

    return $ref;
}

sub ikegami2 {
    my ($ref, @wordsCopy) = @words;

    for my $pos (0..length($ref)) {
       my $letter = substr( $ref, $pos, 1 ); 
       for ( @wordsCopy ) 
       { 
           if ( substr( $_, $pos, 1 ) ne $letter )
           { 
               substr( $ref, $pos, 1, '-' );
               last;
           } 
       }
    }

    return $rv;
}


sub ikegami3 {
    my @wordsCopy;
    push @wordsCopy, [ /./g ]
       for @words;

    my $ref = pop(@wordsCopy);

    for my $pos (0..$#$ref) {
       my $letter = $ref->[$pos]; 
       for ( @wordsCopy ) 
       { 
           if ( $_->[$pos] ne $letter )
           { 
               $ref->[$pos] = '-';
               last;
           } 
       }
    }

    return join '', @$ref;
}