#!/usr/bin/perl -w
use strict;
use Getopt::Long;

#
# A 'Brainfuck' Interpreter by Cal Henderson
# Translation optimisations by Japhy at perlmonks.org
#

#################### ARGS ####################

my ($fromfile,$example,$showsource);
GetOptions ('file' => \$fromfile, 'example' => \$example, 'show' => \$showsource);

if ($fromfile){
	#load program from a file
	open(FH,$ARGV[0]) or die "Can't open source file $ARGV[0]: $!\n";
	$_ = join('',<FH>);
	close(FH);
}elsif ($example){
	#use example program
	$_ = '>+++++++++[<++++++++>-]<++.>++++++[<++++++++>-]<-----.--.+.>++++++++[<---------->-]<----.>+++++++++[<+++++++>-]<++.>++++[<+++>-]<+.+.+++++.>++++[<--->-]<.---.>++++[<+++>-]<+.[-]>++++++++[<++++>-]<.>+++++++[<+++++++>-]<-.>+++++++[<+++>-]<.+++++++++++++.------.[-]>++++++[<++++++>-]<----.>++++++[<+++++++>-]<--.>++++++[<++++>-]<+.++.++++++++.>++[<--->-]<.+++++++++++++.[-]++++++++++.';
}else{
	#explain usage
	die "\nUsage: $0 [-s] -e|(-f filename)\n\n\t-s / --show\tShow perl source listing\n\t-e / --example\tUse example (built-in) program\n\t-f / --file\tLoad program from specified file\n\n";
}

############## THE INTERPRETER ! #############

my ($p,@m);
y/[]<>.,+-//cd;
s/(([+-])\2*)/P$2=@{[length$1]};/g;
s/(([<>])\2*)/Q@{[('+','-')[$2eq'<']]}=@{[length$1]};/g;
s/\./print chrP;/g;
s/,/P=ord getc;/g;
s/\[/while(P){/g;
s/]/}/g;
s/P/\$m[Q]/g;
s/Q/\$p/g;

################### RUN IT ###################

if ($showsource){
	s/;/;\n/g;
	s/}/}\n/g;
	s/{/{\n/g;
	print "===================START OF SOURCE====================\n";
	print;
	print "====================END OF SOURCE=====================\n\n";
}

print "===================START OF OUTPUT====================\n";
eval;
print$@if$@;
print "====================END OF OUTPUT=====================\n";