When we got a lot of values to unpack it's a easy task, since perl allows you to concatenate the templates and unpack then in one call.

But not so lucky when some of the values need list context.
Searching through perlmonks I founded this thread which was almost what I needed, except it unpacks everything in scalar context, so I modified it a bit and here we are: 
sub unpack2hash
{
    my ($template, $source) = @_;
    my $hash = {};
    foreach(split / /,$template)
    {
        my ($temp,$type,$var) = split /:(.)/;
        if($type eq '@')
        {
            my @r = unpack $temp, $source;
            $hash->{$var} = \@r;
            my $pack = pack $temp, @r;
            substr $source, 0, length $pack, '';
        }elsif($type eq '$')
        {
            my $r = unpack $temp, $source;
            $hash->{$var} = $r;
            my $pack = pack $temp, $r;
            substr $source, 0, length $pack, '';
        }
        else{ die "need context type\n" }
    }
    return $hash;
}

[download]
the template syntax is a bit different, see the example: 
my $h = unpack2hash(join(' ',(
'l:$songid',
'c8:@signature',
'l:$genre',
'f:$bpm',
's3:@level',
's:$unk',
'l12:@unk2',
'a24:$genres',
'l2:@unk3',
'a32:$title',
'a32:$subtitle',
'a32:$artist',
'a32:$noter',
'a32:$musicfile',
'l:$jpg',
'l3:@unk4',
'l4:@notepos'
)), $data);

[download]
each value is separated by whitespace, in the format <template>:<context><key>
this way, the values with @ will be unpacked in list context and the values with $ will be unpacked in scalar context, and stored in the hash with its respective key.

UPDATE: I changed the line $source =~ s/$pack//; to substr $source, 0, length $pack, ''; because $pack was being interpreted as a regex.

In reply to Unpacking to hash, with context by Fox

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