while (<>) {
    my ($key,$rest) = split;
    $hash{$key} ||= [];
    push(@{$hash{$key}}, $_);
}

##</code><code>##

(
	243_405 => [ "243_405 35 23 13", "243_405 46 21 15" ],
	241_333 => [ "241_333 65 32 20", "241_333 52 44 11" ]
)

##</code><code>##

------------
:Wq
Not an editor command: Wq