hi perlguyjoe,
Seems I am overwriting my hash, instead of adding a new hash

Am afraid to say you are right. Something like this could show some light, I suppose! 
use warnings;
use strict;
use Data::Dumper;

my %person;
my $key;

while (<DATA>) {
    for ( split /\s+/, $_ ) {
        if (/^(ID)=(.)/) {
            $key = $2;
            $person{$key} = { lc $1 => $2 };
        }
        else {
            my ( $new_key, $value ) = split /=/, $_;
            $person{$key}{ lc $new_key } = $value;
        }
    }
}

print Dumper \%person;

__DATA__
ID=1 First=John Last=Doe AGE=42
ID=2 First=Jane Last=Doe AGE=35
ID=3 First=Jack Last=Doe AGE=17
ID=4 First=Jill Last=Doe AGE=15

[download]
And if I may add see this also perldsc

Update
In fact, you can remove all the drama of if/else within the for loop and do: 
        $key = $1 if /^ID=(.)/;

        my ( $new_key, $value ) = split /=/, $_;
        $person{$key}{ lc $new_key } = $value;

[download]
If you tell me, I'll forget.
If you show me, I'll remember.
if you involve me, I'll understand.
--- Author unknown to me

In reply to Re: Having an Issue updating hash of hashes by 2teez
in thread Having an Issue updating hash of hashes by perlguyjoe

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