#! perl -slw
use strict;

my %stats;

while( <> ) {
    chomp;
    next if length > 8;
    my $word = $_;
    push @{ $stats{ $_ } }, $word for split '', $word;
}

my @freq = sort{
    @{ $stats{ $b } } <=> @{ $stats{ $a } };
} keys %stats;
my %letters; ++$letters{ $_ } for @freq[ 0 .. 7 ];

my %uniq;
for my $l ( keys %letters ) {
    WORD: for my $word ( @{ $stats{ $l } } ) {
        my %letters = %letters;
        for my $c ( split '', $word ) {
            unless( exists $letters{ $c }  and --$letters{ $c } >= 0 ) {
                #print( "rejected: $word" );
                delete $uniq{ $word };
                next WORD ;
            }
        }
        ++$uniq{ $word } ;
    }
}
print "@{[ sort keys %letters ]}: ", scalar keys %uniq;