pack and unpack can handle very many things, but bitfields are not one of them. You'll have to do some bit-level manipulation to extract the values you want; I would recommend you do this: 
$fh->read($buf, 12);
# note that your original code used 's', which is signed,
# but your struct declaration says unsigned!
@var = unpack('S S L L', $buf);
my ($var1, $var2) = ($var[0], $var[1]);
my $var3 = $var[2] & 0xFFFFFF;
my $var4 = $var[2] >> 24;
my $var5 = $var[3] & 0x3F;
my $var6 = $var[3] >> 6;

[download]
--Stevie-O 
$"=$,,$_=q>|\p4<6 8p<M/_|<('=>
.q>.<4-KI<l|2$<6%s!<qn#F<>;$,
.=pack'N*',"@{[unpack'C*',$_]
}"for split/</;$_=$,,y[A-Z a-z]
         {}cd;print lc

[download]

In reply to Re: Unpacking struct by Stevie-O
in thread Unpacking struct by Anonymous Monk

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