while (<STDIN>) {
    $some_hash{$_}++;
}

##</code><code>##

foreach (keys %some_hash) {
    ...some code here...
}

##</code><code>##

my $position = 1;
while (<STDIN>) {
    $myhash{$_}{'item'}++;
    $myhash{$_}{'position'} = $position++ if ! exists $myhash{$_}{'position'};
}