Many ways to do that. Using pack/unpack: 

@ary = map { pack "B32", join "", (1) x $_, (0) x (32 - $_) } 0..31;
print unpack("B*",$_),"\n" for @ary;

[download]

pack"B*" packs a string containing 1 and 0 into binary, unpack does the reverse.

Using vec:

$#ary = 31; # create an array of 32 empty slots
$c = 0; vec($_,0,32) = ~((1<<++$c)-1) for @ary;
@ary = reverse @ary;

# another way without $c
vec($ary[31+$_],0,32) = ~((1<<(-$_+1))-1) for -31..0;

print unpack("B*",$_),"\n" for @ary;

[download]

Both solutions output the table you used for illustration. Now you can use that @ary e.g. to calculate network addresses from address and mask:

@ary = map { pack "B32", join "", (1) x $_, (0) x (32 - $_) } 0..31;
$dotted    = "192.168.248.17";
$netmask   = $ary[19]; # prefix 19, i.e. cidr 192.168.248.17/19
$address   = pack "C4", split /\./, $dotted;
$network   = $address & $netmask;
$broadcast = $address | ~ $netmask;
print $_,$/ 
  for map {
    join ".", unpack "C4", $_
  } $netmask, $address, $network, $broadcast;
__END__
255.255.224.0
192.168.248.17
192.168.224.0
192.168.255.255

[download]

Both your example table and those created with the above snippets lack the last element having all 32 bits set, which corresponds to prefix 32, i.e. $address == $network == $broadcast with netmask 255.255.255.255 - fixing that is left as an excercise for the reader.

update: ...a golfed CIDR calculator:

#!/usr/bin/perl
# file cidr
$m=pack B32,pop=~'/'x$';printf"$` network %vd broadcast %vd netmask %v
+d\n",($z=eval$`)&$m,$z|~$m,$m

[download]
qwurx [shmem] ~> cidr 192.168.248.17/19
192.168.248.17 network 192.168.224.0 broadcast 192.168.255.255 netmask
+ 255.255.224.0

[download]
perl -le'print map{pack c,($-++?1:13)+ord}split//,ESEL'

In reply to Re: vec vs pack/unpack by shmem
in thread vec vs pack/unpack by Anonymous Monk

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