Looks like homework, but anyway. My stab is a little more defensive and allows multiple (0 .. n) values per key

use Data::Peek;
my %d;
while (<DATA>) {
    s/^\s*>?\s*(.*?)[\s\r\n]*\z/$1/;
    m/^(\d+)$/ ? push @{$d{$a}} => $1 : ($a = $_);
    }
DDumper \%d;

__END__
>James
>40 
>James
>35
>James
>26
>James
>15
James
10
>12
>Philip
10
4
>5
Philip
James
Philip
18
[download]

->

{   James            => [
        '40',
        '35',
        '26',
        '15',
        '10',
        '12'
        ],
    Philip           => [
        '10',
        '4',
        '5',
        '18'
        ]
    }
[download]