hello_world.txt

#!/usr/bin/env PeanutButterJellyTime
# -----------------------------------------------------------------------------
# keyword => C equiv            (description)
# -----------------------------------------------------------------------------
# peanut  => ++*ptr             (increase value of cell)
# PEANUT  => ++ptr              (move to next cell)
# butter  => --*ptr             (decrease value of cell)
# BUTTER  => --ptr              (move to previous cell)
# jelly   => putchar(*ptr)      (print character value of cell)
# JELLY   => *ptr=getchar()     (store numeric value of char input in cell)
# time    => while (*ptr) {     (start loop block that loops while the current
#                                cell is non-zero)
# TIME    => }                  (end loop block)

# -----------------------------------------------------------------------------
# "Hello World!" written in "peanut butter jelly time" brainfuck variant
# -----------------------------------------------------------------------------

# initialize cell 0 to 10 to act as a loop counter
peanut peanut peanut peanut peanut
peanut peanut peanut peanut peanut
# current cell: 0

# set up cells for upper|lower|punctuation|newline
# start loop block
time

  # move to cell 1
  PEANUT
  # add 7
  peanut peanut peanut peanut peanut
  peanut peanut
  # current cell: 1
  
  # move to cell 2
  PEANUT
  # add 10
  peanut peanut peanut peanut peanut
  peanut peanut peanut peanut peanut
  # current cell: 2
  
  # move to cell 3
  PEANUT
  # add 3
  peanut peanut peanut
  # current cell: 3
  
  # move to cell 4 
  PEANUT
  # add 1
  peanut
  # current cell: 4
  
  # decrement loop counter
  # move to cell 0
  BUTTER BUTTER BUTTER BUTTER
  # subtract 1
  butter
  # current cell: 0

# end loop block
TIME
# cells should now be: 0|70('F')|100('d')|30(RS)|10(NL)

# print 'H'
# move to cell 1
PEANUT
# add 2
peanut peanut
# cells should now be 0|72('H')|100('d')|30(RS)|10(NL)
# print char value
jelly

# print 'e'
# move to cell 2
PEANUT
# add 1
peanut
# cells should now be 0|72('H')|101('e')|30(RS)|10(NL)
# print char value
jelly

# print 'l'
# add 7 to cell 2
peanut peanut peanut peanut peanut
peanut peanut
# cells should now be 0|72('H')|108('l')|30(RS)|10(NL)
# print char value
jelly

# print 'l' again
jelly

# print 'o'
# add 3 to cell 2
peanut peanut peanut
# cells should now be 0|72('H')|111('o')|30(RS)|10(NL)
# print char value
jelly

# print ' '
# move to cell 3
PEANUT
# add 2
peanut peanut  
# cells should now be 0|72('H')|111('o')|32(' ')|10(NL)
# print char value
jelly

# print 'W'
# move to cell 1
BUTTER BUTTER
# add 15
peanut peanut peanut peanut peanut
peanut peanut peanut peanut peanut
peanut peanut peanut peanut peanut
# cells should now be 0|87('W')|111('o')|32(' ')|10(NL)
# print char value
jelly

# print 'o'
# move to cell 2
PEANUT
# print char value
jelly

# print 'r'
# add 3 to cell 2
peanut peanut peanut
# cells should now be 0|87('W')|114('r')|32(' ')|10(NL)
# print char value  
jelly

# print 'l'
# subtract 6 from cell 2
butter butter butter butter butter  
butter
# cells should now be 0|87('W')|108('l')|32(' ')|10(NL)
# print char value
jelly

# print 'd'
# subtract 8 from cell 2
butter butter butter butter butter  
butter butter butter
# cells should now be 0|87('W')|100('d')|32(' ')|10(NL)
# print char value
jelly

# print '!'
# move to cell 3
PEANUT
# add 1
peanut
# cells should now be 0|87('W')|100('d')|33('!')|10(NL)
# print char value 
jelly

# print newline
# move to cell 4
PEANUT
# print char value
jelly

pbjt.c

#include "pbjt.h"

void interpret(char *itape)
{
    char *iop = itape;
    
    while (*iop) {
        switch (*iop) {
            case NOP:
                return;
                break;
            case INC_CELL:
                ++*cell;
                ++iop;
                break;
            case DEC_CELL:
                --*cell;
                ++iop;
                break;
            case NEXT_CELL:
                ++cell;
                ++iop;
                break;
            case PREV_CELL:
                --cell;
                ++iop;
                break;
            case PUT_CELL:
                putchar(*cell);
                ++iop;
                break;
            case GET_CELL:
                *cell = getchar();
                ++iop;
                break;
            case START_LOOP:
                ++iop;
                char ltape[MAX_OPS];
                char *lop = ltape;
                while (*iop != END_LOOP) {
                    *lop = *iop;
                    ++lop;
                    ++iop;
                }
                while (*cell) {
                    interpret(ltape);
                }
                break;
            case END_LOOP:
                ++iop;
                break;
        }
    }
}

pbjt.h

#ifndef PeanutButterJellyTime_pbjt_h
#define PeanutButterJellyTime_pbjt_h

#include <stdio.h>

enum tokens {
    NOP = 0,
    INC_CELL,
    DEC_CELL,
    NEXT_CELL,
    PREV_CELL,
    PUT_CELL,
    GET_CELL,
    START_LOOP,
    END_LOOP
};

#ifndef MAX_CELLS
#define MAX_CELLS 30000
#endif

#ifndef MAX_OPS
#define MAX_OPS 1048576
#endif

char cells[MAX_CELLS];
char *cell;
char tape[MAX_OPS];
char *op;

void interpret(char *itape);

#endif

pbjt.l

%{
  #include "pbjt.h"
%}

%option nodefault
%option noyywrap
%option align
%option full
%option warn
%option batch

comment #[^\n]*\n
ws [ \t\r\n]+

%%
{comment}   { /* Ignore comment */ }
{ws}        { /* Ignore white spaces */ }

"peanut"    { *op = INC_CELL;   ++op; }
"PEANUT"    { *op = NEXT_CELL;  ++op; }
"butter"    { *op = DEC_CELL;   ++op; }
"BUTTER"    { *op = PREV_CELL;  ++op; }
"jelly"     { *op = PUT_CELL;   ++op; }
"JELLY"     { *op = GET_CELL;   ++op; }
"time"      { *op = START_LOOP; ++op; }
"TIME"      { *op = END_LOOP;   ++op; }
%%

int main(int argc, char **argv)
{
  if(argc > 1) {
    if(!(yyin = fopen(argv[1], "r"))) {
      perror(argv[1]);
      return (1);
    }
  }
  
  cell = cells;
  op = tape;
  yylex();
  interpret(tape);
}

$ lex pbjt.l
pbjt.l:27: warning, -s option given but default rule can be matched
$ ls
hello_world.txt lex.yy.c        pbjt.c          pbjt.h          pbjt.l
$ cc -o pbjt lex.yy.c pbjt.c
$ ./pbjt < hello_world.txt
Hello World!