Hidden stereogram message

TeX 212

I am using a typesetting system, not ASCII. The column width can be changed by changing 90pt in the fourth line, but I don't know if that's enough to qualify for the 50 bytes discount. The distance between the two copies of the text can be changed by changing the 9pt, also in the fourth line. The code can probably be made shorter. One can replace each newline by a single space, but not remove them completely.

\let\e\expandafter\read5to\t\read5to\.\def\a#1
{\def\~##1#1##2\a{\def\t{##1\hbox{\
#1\~{}}##2}\a}\e\~\t\a}\e\a\.{}\shipout\hbox
spread9pt{\hsize90pt\fontdimen3\font\hsize\vbox{\t}\
\let\~\ \def\ {}\vbox{\t}}\end.

After calling tex filename.tex in the terminal, the user is prompted to give the main text, then prompted again for a list of words to shift. No empty line in between. The (space-separated) list of words given in the second line should appear exactly as it is in the main text (punctuation is treated just like a letter would be, only spaces delimit words).

Javascript 391 (441 - 50)

(My first code golf)

k=' ';Q='length';A=prompt().split(k);S=prompt().split(k);i=-1;M=25;L=[[]];j=0;R='';while(i++<A[Q]-1){if((j+A[i][Q])<M){if(S.indexOf(A[i])>-1){A[i]=(j?k+k:k)+A[i]}L[L[Q]-1].push(A[i]);j+=A[i][Q]+1}else{j=0;i--;L.push([])}}for(i=0;i<L[Q]-1;P(L[i++].join(C))){C=k;while(L[i].join(C+k)[Q]<M){C+=k}}P(L[i].join(k)+k);function P(a){while(a[Q]<M){a=a.replace(k,k+k)}R+=a;for(c in S){a=a.split(k+k+S[c]).join(k+S[c]+k)}R+=k+k+a+'\n'}console.log(R);

Result

In    a  little  district   In    a  little  district
west    of     Washington   west    of    Washington 
Square   the streets have   Square   the streets have
run    crazy  and  broken   run    crazy  and  broken
themselves    into  small   themselves    into  small
strips   called 'places'.   strips   called 'places'.
These     'places'   make   These     'places'   make
strange     angles    and   strange     angles    and
curves.     One    Street   curves.     One    Street
crosses  itself a time or   crosses  itself a time or
two.     An  artist  once   two.     An  artist  once
discovered    a  valuable   discovered    a  valuable
possibility     in   this   possibility     in   this
street.      Suppose    a   street.      Suppose    a
collector   with  a  bill   collector   with  a  bill
for   paints,  paper  and   for  paints ,  paper  and
canvas      should,    in   canvas      should,    in
traversing   this  route,   traversing   this  route,
suddenly   meet   himself   suddenly   meet  himself 
coming    back, without a   coming    back, without a
cent  having been paid on   cent  having been paid on
account!                    account! 

Long code:

var arr = "In a little district west of Washington Square the streets have run crazy and broken themselves into small strips called 'places'. These 'places' make strange angles and curves. One Street crosses itself a time or two. An artist once discovered a valuable possibility in this street. Suppose a collector with a bill for paints, paper and canvas should, in traversing this route, suddenly meet himself coming back, without a cent having been paid on account!".split(' ');
var secret = "Washington paints himself".split(' ');
var i = -1;
var MAX_WIDTH = 25;
var lines = [[]];
var _l = 0;

var result = '';

while (i++ < arr.length - 1) {
    if ((_l + arr[i].length) < MAX_WIDTH) {
        if (secret.indexOf(arr[i]) > -1) {arr[i] = (_l?'  ':' ') + arr[i]}
        lines[lines.length - 1].push(arr[i]);
        _l += arr[i].length + 1;

    } else {
        _l = 0;
        i--;
        lines.push([]);
    }
}

for (var i = 0; i < lines.length - 1; putText(lines[i++].join(chars))) {
  // Align text
  var chars = ' ';
  while (lines[i].join(chars + ' ').length < MAX_WIDTH) {
    chars += ' ';
  }
}
putText(lines[i].join(' ') + ' ');
function putText(line) {
  while (line.length < MAX_WIDTH) {
    line = line.replace(' ', '  ');
  }
  // Make the illusion
  result += line;
  for (var val in secret) {
    line = line.split('  '+secret[val]).join(' ' + secret[val] + ' ');
  }
  result += ('   ' + line) + '\n';
}
console.log(result);

Javascript 493 (minimum expectations)

g=" ";l=prompt().split(g);r=l.slice();m=prompt().split(g);f=[];s=f.slice();w=0;n=0;a="";for(i=0;i<l.length;i++){if(l[i]==m[0]){m.shift();l[i]=g+r[i];r[i]+=g;}if(l[i].length+1>w)w=l[i].length+1;}while(l.length){f[f.length]="";s[s.length]="";while(l.length&&f[f.length-1].length+l[0].length<w){f[f.length-1]+=l[0]+g;s[s.length-1]+=r[0]+g;l.shift();r.shift();}f[f.length-1]+=g.repeat(w-f[f.length-1].length);}console.log(f,s);while(f.length){a+=f[0]+s[0]+"\n";f.shift();s.shift();}console.log(a);

This code sets up two arrays of lines (left and right), arranges them in a string and prints to f12 console.

_{This is just a minimum answer, not intended to win.}