$fh->read($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;

##</code><code>##

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