vec EXPR, OFFSET, BITS

The vec function provides a compact storage of lists of
unsigned integers. These integers are packed as tightly as
possible within an ordinary perl string. EXPR is treated as a 
bit string. OFFSET specifies the index of the particular 
element. BITS specifies how wide each element is in bits.

Your JAPH does not run on my system, output:

jtjt `jjt``j j`jj ```j`j

cheers

tachyon
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The question was rhetorical :p

Do you have a dbcs? All my JAPH does is reverse the two bit-words of each character.

Or perhaps your $?, $^F or $| don't default as mine do.

try this version with hard coded constants:



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

$_="011291020310415102805081036150812103801030115081";
s/(..)/\\x$1/g;eval"\$_=\"$_\";";print,if($_=join'',map{
chr((vec($_,0,4).vec($_,1,4))+96)}split//)=~s;~; ;g;
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Different defaults it was, hard coded ran fine, but made the 
dissection less obfu :-(

On my box $| is the problem, $| is 1, which flushes
your JAPH too :-)

print"\$?:$? \$^F:$^F \$|:$|\n";
$?:0 $^F:2 $|:1

So this runs

$_="011291020310415102805081036150812103801030115081";
s/(..)/\\x$1/g;eval"\$_=\"$_\";";print,if($_=join'',map{
chr((vec($_,$?,2*$^F).vec($_,$|,4))+96)}split//)=~s;~; ;g;


Disection follows (of the hard code) now that the use of:
$?:0 $^F:2 $|:1 has been let out of the bag

tachyon

# this is what vec is
#
# another running dissection by tachyon
#
# code string
$_="011291020310415102805081036150812103801030115081";

#  this line grabs pairs from $_ and add hex escapes
s/(..)/\\x$1/g;
# this gives:
# $_='\x01\x12\x91\x02\x03\x10\x41\x51\x02\x80\x50\x81\x03\x61\x50\x81
+\x21\x03\x80\x10\x30\x11\x50\x81';

# the function of this line is to convert the hex 
# escapes to their ascii representation due to the
# interpolation that occurs to $_
eval"\$_=\"$_\";";

# the code below summarises these two steps
# but it is now more obvious what is going on
# uncomment it and this still runs so it must be right!
# $_="011291020310415102805081036150812103801030115081";
# $_ =~ s/(..)/chr hex $1/eg;

# I will rearrange this to make it easier to understand
print, if($_=join'',map{chr((vec($_,0,4).vec($_,1,4))+96)}split//)=~s;
+~; ;g;

# first lets reset $_ using my shortened code
$_="011291020310415102805081036150812103801030115081";
$_ =~ s/(..)/chr hex $1/eg;

# split up our chars
@ascii = split//,$_;

#now we replace the map with this boring loop
for (@ascii) {
    push @decode, chr((vec($_,0,4).vec($_,1,4))+96);
}

# join the decoded chars
$_ = join'', @decode;

# sub out the ~ chars  s/~/ /g  tr/~/ /
s;~; ;g;

#print it 
print "\n$_";

# so now all we need to understand is what vec does:
#
# vec EXPR, OFFSET, BITS
#
# The vec function provides a compact storage of lists of
# unsigned integers. These integers are packed as tightly as
# possible within an ordinary perl string. EXPR is treated as a 
# bit string. OFFSET specifies the index of the particular 
# element. BITS specifies how wide each element is in bits.
#
# So what happens is that for each eight bits we grab two
# nybbles (4 bits) giving us 0-15 decimal after 'vec'ing.
# we concat these together, run that through chr and
# bob's your uncle
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