#!/usr/bin/perl -sw
     
    die unless $book;
    my $filename = $book;
    $book =~ s/\.ps$//i;
     
    print "realigning pages...\n";
    system "psbook -s4 $filename > $book-tempA.ps";
     
    print "\nmerging pages...\n";
    system "psnup -2 $book-tempA.ps > $book-tempB.ps";
     
    system "rm $book-tempA.ps";
    print "\nwriting front sides...\n";
     
    system "psselect -o $book-tempB.ps > $book-FRONT.ps";
     
    print "\nwriting back sides...\n";
    system "psselect e- $book-tempB.ps < $book-BACK.ps";
     
    system "rm $book-tempB.ps";