You want unpack "B*" (not unpack "b*"), and it requires packed bytes.
$ perl -Mv5.14 -e'
my $scabyte = 0x41;
say unpack "B*", pack "C*", $scabyte;
'
01000001
When you already have unpacked bytes, you can use sprintf "%b".
$ perl -Mv5.14 -e'
my $scabyte = 0x41;
say sprintf "%08b", $scabyte;
'
01000001
#!/usr/bin/perl
use v5.14;
use warnings;
my $packed_bytes = "ABCD";
my @bytes = unpack 'C*', $packed_bytes;
my $bin = '';
for my $byte ( @bytes ) {
printf "Decimal = [%1\$d] Hex = [%1\$02X] Binary = [%1\$08b]\n",
$byte;
$bin .= sprintf( "%08b", $byte );
}
say "";
say $bin;
Decimal = [65] Hex = [41] Binary = [01000001]
Decimal = [66] Hex = [42] Binary = [01000010]
Decimal = [67] Hex = [43] Binary = [01000011]
Decimal = [68] Hex = [44] Binary = [01000100]
01000001010000100100001101000100
#!/usr/bin/perl
use v5.14;
use warnings;
my $packed_bytes = "ABCD";
my $bin = unpack "B*", $packed_bytes;
say $bin;
01000001010000100100001101000100
