##
dd if=/dev/hdb0 | strings -n 10 | grep -i secretkey
####
my $pid = open(FH, " dd if=/dev/hdb0 | ") or die "$!\n";
while( my $rrv = sysread( FH, my $buf, 1012 ) ){
#regex your $buf here for whatever
#of course you will have to worry about missing full strings
#on your chunk boundaries, so you may need to save a few
#hunderd bytes of each $buf to add to the next one
}