use Data::Dumper;
while(<DATA>){
    chomp;
    my ($email,$domain) = split /\t/;
    push @{$hash{$domain}},$email;
}
print join "\n", keys %hash,"\n";
print "Email:",$hash{'yahoo.com'}[0].'@yahoo.com';

__DATA__
ahlnpstx    gmail.com
dghjklorsvwy    hotmail.com
cdegijlmqrstvwxz    yahoo.com
abegijknostv    yahoo.com
abcefghjlqrtuyz    hotmail.com
acghiknoprux    hotmail.com
abceghlmrstwxy    gmail.com
cdehiklmnqtwxyz    gmail.com
bdjklmortvw    hotmail.com
bdegjkmrsuxz    gmail.com
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