#!/usr/bin/perl
use Data::Dumper;          # only for teaching purpose
$Data::Dumper::Indent = 1; # dito :-)

while(<DATA>) {
    chop;
    my($familyname,$memberstring) = split /\s--\s/,$_;
    my @members = split /, /,$memberstring;
    # tell each member that it's got a new family
    foreach my $member(@members) {
        push(@{$family{$member}},$familyname);
    } 
} 
print Dumper(\%family); # show the data structure in %family
# now output a list of members with their families
foreach my $member(sort keys %family) {
    print "$member can be found " . scalar(@{$family{$member}}) . ": "
        . join(" ", @{$family{$member}}) . "\n";
}