To see your program as Perl sees it, deparse it:

c:\@Work\Perl\monks>perl -wMstrict -MO=Deparse,-p -e
"print 'Enter decimal number less than 256: ';
 my $decimal;
 $decimal=<STDIN>;
 chomp $decimal;
 print $decimal & 128 <=> 0;
 print $decimal &  64 <=> 0;
 print $decimal &  32 <=> 0;
 print $decimal &  16 <=> 0;
 print $decimal &   8 <=> 0;
 print $decimal &   4 <=> 0;
 print $decimal &   2 <=> 0;
 print $decimal &   1 <=> 0;
"
BEGIN { $^W = 1; }
use strict 'refs';
print('Enter decimal number less than 256: ');
my($decimal);
($decimal = <STDIN>);
chomp($decimal);
print(($decimal & 1));
print(($decimal & 1));
print(($decimal & 1));
print(($decimal & 1));
print(($decimal & 1));
print(($decimal & 1));
print(($decimal & 1));
print(($decimal & 1));
-e syntax OK
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Update: Why does every expression like  128 <=> 0 become the constant 1? Because the Perl compiler, like most compilers today, is smart enough to know that the result of the comparison of a constant to a constant is just going to be yet another constant, 1 in all these cases. (Update: I believe this process is called constant folding.)

use warnings;
use strict;

print "Enter decimal number less than 256:"; 
my $decimal; 
$decimal=<STDIN>; 
chomp $decimal; 
printf '%08b', $decimal; 
print "\n";
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You have a precedence problem. Modify your print lines to be: print +( $decimal & nnn ) <=> 0;

What is it about the value '255' that allows the program to work correctly ?

$ perl -E 'say 254 & 2 <=> 0'
0
$ perl -E 'say 255 & 2 <=> 0'
1
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        "Despite my privileged upbringing, I'm actually quite well-balanced. I have a chip on both shoulders."         - John Nash

What is it about the value '255' that allows the program to work correctly ?

255 has all ones. Thus if the program tests the same bit and prints 1, 8 times it just looks like it worked.

It didn't. Any value that has the first bit set will also produce a 1:

say 253 & 2 <=> 0;;
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Using the OPs original code, the fact that only the first bit is being tested becomes obvious when you enter a 1:

C:\test>perl

#!/usr/bin/perl -w
use strict;
use warnings;

print "Enter decimal number less than 256:";
my $decimal;
$decimal=<STDIN>;
#chomp $decimal;
print $decimal & 128 <=> 0;
print $decimal & 64 <=> 0;
print $decimal & 32 <=> 0;
print $decimal & 16 <=> 0;
print $decimal & 8 <=> 0;
print $decimal & 4 <=> 0;
print $decimal & 2 <=> 0;
print $decimal & 1 <=> 0 ;
^Z
Enter decimal number less than 256:1
11111111
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And the fact that 255 appeared to work, is just coincidence.

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority". I'm with torvalds on this

In the absence of evidence, opinion is indistinguishable from prejudice. Agile (and TDD) debunked

What is it about the value '255' that allows the program to work correctly?

Even a stopped clock is right twice a day.

Odd, isn't it? .-)

Hi there

please try this version of your code, it worked for me ^_^

#!/usr/bin/perl -w 
use strict; 
use warnings; 

print "Enter decimal number less than 256:"; 
my $decimal; 
$decimal=<STDIN>; 
chomp $decimal; 
# $decimal += 0;
print (($decimal & 0x80) <=> 0); 
print (($decimal & 0x40) <=> 0); 
print (($decimal & 0x20) <=> 0); 
print (($decimal & 0x10) <=> 0); 
print (($decimal & 0x08) <=> 0); 
print (($decimal & 0x04) <=> 0); 
print (($decimal & 0x02) <=> 0); 
print (($decimal & 0x01) <=> 0);
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What is the reason for the n <=> 0 comparison?

---

Give a man a fish:  <%-(-(-(-<

The usage for <=> here in the masking expreasion ($decimal & 0x80) is to test if this 8th bit is zero or one, also you can do it like:

#!/usr/bin/perl -w 
use strict; 
use warnings; 

print "Enter decimal number less than 256:"; 
my $decimal; 
$decimal=<STDIN>; 
chomp $decimal; 
# $decimal += 0;
print (($decimal & 0x80)? (1) : (0) );    # to test the 8th bit
print (($decimal & 0x40)? (1) : (0) );    # to test the 7th bit
print (($decimal & 0x20)? (1) : (0) );    # to test the 6th bit
print (($decimal & 0x10)? (1) : (0) );    # to test the 5th bit
print (($decimal & 0x08)? (1) : (0) );    # to test the 4th bit
print (($decimal & 0x04)? (1) : (0) );    # to test the 3th bit
print (($decimal & 0x02)? (1) : (0) );    # to test the 2nd bit
print (($decimal & 0x01)? (1) : (0) );    # to test the 1st bit
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