broken output

>>> m('?@$..!!+.!!+>!.!!!!+?/!!!@!@>!!!')
pushing 0
[0]
pushing say_1
[0, (1, 'say_1')]
pushing call_2
[0, (1, 'say_1'), (2, 'call_2')]
pushing chain_2
[0, (1, 'say_1'), (2, 'call_2'), (2, 'chain_2')]
pushing chain_2
[0, (1, 'say_1'), (2, 'call_2'), (2, 'chain_2'), (2, 'chain_2')]
function chain_2 acting on chain_2
[0, (1, 'say_1'), (2, 'call_2'), (1, 'partial_chain_2_chain_2')]
function partial_chain_2_chain_2 acting on call_2
pushing composition_n for chain_2 and call_2
[0, (1, 'say_1'), (2, 'composition_n')]
pushing clone_1
[0, (1, 'say_1'), (2, 'composition_n'), (1, 'clone_1')]
pushing chain_2
[0, (1, 'say_1'), (2, 'composition_n'), (1, 'clone_1'), (2, 'chain_2')]
function chain_2 acting on clone_1
[0, (1, 'say_1'), (2, 'composition_n'), (1, 'partial_chain_2_clone_1')]
function partial_chain_2_clone_1 acting on composition_n
pushing composition_n for clone_1 and composition_n
[0, (1, 'say_1'), (1, 'composition_n')]
pushing clone_1
[0, (1, 'say_1'), (1, 'composition_n'), (1, 'clone_1')]
pushing shift_1
[0, (1, 'say_1'), (1, 'composition_n'), (1, 'shift_1')]
function shift_1 acting on composition_n
shifting composition_n
[0, (1, 'say_1'), (2, 'shifted_n')]
pushing chain_2
[0, (1, 'say_1'), (2, 'shifted_n'), (2, 'chain_2')]
function chain_2 acting on shifted_n
[0, (1, 'say_1'), (1, 'partial_chain_2_shifted_n')]
function partial_chain_2_shifted_n acting on say_1
pushing composition_n for shifted_n and say_1
[0, (2, 'composition_n')]
function composition_n acting on 0
[(1, 'partial_composition_n_0')]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "shift.py", line 86, in m
    i(e[_])
  File "shift.py", line 13, in i
    def i(x):x(*[o() for _ in j(x)]) #pop args, call func 
IndexError: pop from empty list

shift.py

import pdb

def m_ungolfed(t):
    from functools import partial as b #this is our currier
    k,d=[],[] #stack, output string
    u,o=k.append,k.pop #push & pop
    w=lambda x:x is 0 #quick checker for func vs blank
    j=lambda x:range(x.a) #iterate over arity
    nm = lambda x:x.__name__ if not w(x) else str(x) #debugging
    def a(n): #decorator to assign an arity to a function
        def f(x):x.a=n;return x
        return f
    def i(x):x(*[o() for _ in j(x)]) #pop args, call func 
    @a(2)
    def apply_2(x,y):
        print 'function '+nm(x)+' acting on '+nm(y)
        #x(y) if x.a==1 else u(a(x.a-1)(b(x,y)))
        if x.a==1:
            x(y)
        else:
            _ = a(x.a-1)(b(x,y))
            _.__name__ = 'partial_'+nm(x)+'_'+nm(y)
            u(_) #p
    @a(0)
    def blank_0():
        print 'pushing 0'
        u(0) #q
    @a(0)
    def c():
        print 'pushing clone_1'
        @u
        @a(1)
        def clone_1(x):
            print 'cloning '+nm(x)
            u(x);u(x) #f
    @a(0)
    def v():
        print 'pushing shift_1'
        @u
        @a(1)
        def shift_1(x): #y
            print 'shifting '+nm(x)
            @u
            @a(x.a+1)
            def shifted_n():_=o();i(x);u(_) #f
    @a(0)
    def r():
        print 'pushing fork_3'
        @u
        @a(3)
        def fork_3(x,y,z):
            print 'x is '+nm(x)+', so push '+[nm(y),nm(z)][w(x)]
            u(y if w(x) else z) #f
    @a(0)
    def l(): #u(p)
        print 'pushing call_2'
        @u
        @a(2)
        def call_2(x,y):
            print 'function '+nm(x)+' acting on '+nm(y)
            x(y)if x.a==1 else u(a(x.a-1)(b(x,y)))
    @a(0)
    def n():
        print 'pushing chain_2'
        @u
        @a(2)
        def chain_2(x,y):#f
            print 'pushing composition_n for '+nm(x)+' and '+nm(y)
            @u
            @a(x.a)
            def composition_n(*_):
                pdb.set_trace()
                print type(nm(y)), type(y)
                print 'calling '+nm(x)+' then '+nm(y)
                x(*_);i(y)#h
    @a(0)
    def s():
        print 'pushing say_1'
        @u
        @a(1)
        def say_1(x):
            print 'x is '+nm(x)+', so saying '+['1','0'][w(x)]
            d.append(['1','0'][w(x)]);u(x)#f
    #e=dict(zip('!?+>/$.@',[p,q,c,v,r,l,n,s]))
    e=dict(zip('!?+>/$.@',[apply_2,blank_0,c,v,r,l,n,s]))
    for _ in t:
        try:
            i(e[_])
        except RuntimeError:
            break
        print [(_.a,nm(_)) if not w(_) else _ for _ in k]
    print ''.join(d)

working output

>>> m('?@!@@!')
pushing 0
[0]
pushing say_1
[0, (1, 'say_1')]
function say_1 acting on 0
x is 0, so saying 0
[0]
pushing say_1
[0, (1, 'say_1')]
pushing say_1
[0, (1, 'say_1'), (1, 'say_1')]
function say_1 acting on say_1
x is say_1, so saying 1
[0, (1, 'say_1')]
01