#!/usr/local/bin/perl -l
use strict; 
my $working; 
my @rules; 
my $rulecount=0; 
my $temp; 
my $temp2; 
my $doubling=0; 
# If a Y is given as the first argument, double each element of the output to 
# show the similarity to system 5 
$ARGV[0]eq'Y' and do{$doubling=1; shift @ARGV;}; 
# Read from file 
$ARGV[0]eq'F' and do{ 
    shift @ARGV; 
    my $file = shift @ARGV; 
    local $/ = undef; 
    open INFILE, $file; 
    @ARGV = split(' ',<INFILE>); 
    close INFILE; 
}; 
$|=1; 
# Load the working string 
$working=shift @ARGV; 
chomp $working; 
# Load the rules 
for my $e (@ARGV) 
{ 
    chomp $e; 
    $e eq '""' and $e = ''; 
    $rules[$rulecount++]=$e; 
} 
while($working ne '') 
{ 
    # Remove and print the first element of the working string 
    $temp=substr $working,0,1,''; 
    print $temp; 
    $doubling and print $temp; 
    push @rules, ($temp2 = shift @rules); 
    $temp eq '1' and $working .= $temp2; 
} 
print "\n";