use Data::Dumper;

my @lines = (
    ['_W9C2JJDCB', 'asdf1', 'zxcv1', ],
    ['_W9C2JJDCB', 'asdf2', 'zxcv2', ],
    ['_W9C2JJDCB', 'asdf3', 'zxcv3', ],
);
my %hash = (
    '_W9C2JJDCB' => [
        '_W92CJJDCB',
        '201200240',
        'TEST: IGNORE',
        'John Doe',
        'Closed',
        'HIP',
        'email@email.com',
        'email2@email.com',
    ],
);

foreach my $key (keys %hash) {
    foreach my $line (@lines) {
        if ($line->[0] eq $key) {
            shift @$line;
            push @{$hash{$key}}, @$line;
        }
    }
}

die Dumper(%hash);