Actually, if you only want to output the data the way you've shown, then you could do it without nested data structure and use a simple hash (or a simple array), provided you concatenate the values into the hash as you go (re-using part of AnomalousMonk's code):

$ perl -wMstrict -MData::Dumper -e 'my $pair = qr{ (\d+) \s+ ([[:alpha
+:]]+) }xms;
> my $record = "1 A 1 B 2 G 2 H 2 V";
> my %hash;
> while ($record =~ m{ \G \s* $pair }xmsg) {
>    $hash{$1} .= "$2;";
> }
> print Dumper \%hash;
> '
$VAR1 = {
          '1' => 'A;B;',
          '2' => 'G;H;V;'
        };
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