in reply to Why is this code so much slower than the same algorithm in C?

Let's look at what is really going on when these programs run.

  1. First the C program. It translates into the following assembler:
    <Reveal this spoiler or all spoilers in this node or all in this thread>
  2. Now the Perl code. It translates into the following ... um...I terrified to apply a term to this because one or more of the local language laywers is going to leap all over what ever term I use to say that it isn't really 'term' because blah, blah, ... more irrelavancies, ... blah!

    So, whatever terms suits you, which may include one of the following: <opcodes|bytecode|syntax tree|abstract syntax tree|other>.

    (Dodge issue!) This is the output from perl -MO=Concise YourScript.pl: 

    1k <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 1 junk2.pl:2) v ->3
6     <@> list vKPM/128 ->7
3        <0> pushmark vM/128 ->4
4        <0> padsv[$i:1,8] vM/LVINTRO ->5
5        <0> padsv[$j:1,8] vM/LVINTRO ->6
7     <;> nextstate(main 7 junk2.pl:13) v ->8
a     <2> sassign vKS/2 ->b
8        <$> const[IV 20] s ->9
9        <0> padsv[$i:1,8] sRM* ->a
-     <@> lineseq vK ->1k
b        <;> nextstate(main 7 junk2.pl:4) v ->c
1j       <2> leaveloop vK/2 ->1k
c           <{> enterloop(next->1f last->1j redo->d) v ->d
-           <@> lineseq vK ->1j
1e             <@> leave vKP ->1f
d                 <0> enter v ->e
e                 <;> nextstate(main 3 junk2.pl:7) v ->f
h                 <2> sassign vKS/2 ->i
f                    <$> const[IV 1] s ->g
g                    <0> padsv[$j:1,8] sRM* ->h
-                 <@> lineseq vK ->10
i                    <;> nextstate(main 3 junk2.pl:5) v ->j
z                    <2> leaveloop vK/2 ->10
j                       <{> enterloop(next->s last->z redo->k) v ->v
-                       <1> null vK/1 ->z
y                          <|> and(other->k) vK/1 ->z
x                             <2> lt sK/2 ->y
v                                <0> padsv[$j:1,8] s ->w
w                                <$> const[IV 20] s ->x
-                             <@> lineseq vK ->-
r                                <@> leave vKP ->s
k                                   <0> enter v ->l
l                                   <;> nextstate(main 2 junk2.pl:6) v
+ ->m
-                                   <1> null vK/1 ->r
p                                      <|> and(other->q) vK/1 ->r
o                                         <2> modulo[t5] sKP/2 ->p
m                                            <0> padsv[$i:1,8] s ->n
n                                            <0> padsv[$j:1,8] s ->o
q                                         <0> last v* ->r
t                                <1> preinc[t4] vK/1 ->u
s                                   <0> padsv[$j:1,8] sRM ->t
u                                <0> unstack v ->v
10                <;> nextstate(main 6 junk2.pl:9) v ->11
-                 <1> null vKP/1 ->1e
14                   <|> and(other->15) vK/1 ->1e
13                      <2> eq sK/2 ->14
11                         <0> padsv[$j:1,8] s ->12
12                         <$> const[IV 20] s ->13
1d                      <@> leave vKP ->1e
15                         <0> enter v ->16
16                         <;> nextstate(main 4 junk2.pl:10) v ->17
1a                         <@> prtf vK ->1b
17                            <0> pushmark s ->18
18                            <$> const[PV "Number: %d\n"] s ->19
19                            <0> padsv[$i:1,8] l ->1a
1b                         <;> nextstate(main 4 junk2.pl:11) v ->1c
1c                         <0> last v* ->1d
1h             <2> add[t3] vKS/2 ->1i
1f                <0> padsv[$i:1,8] sRM ->1g
1g                <$> const[IV 20] s ->1h
1i             <0> unstack v ->d

    [download]

    And within that, there is one line: o                             <2> modulo[t5] sKP/2 ->p

    which is the equivalent of these four assembly instructions from the C version: 

    ; Line 8
        mov     eax, DWORD PTR _i$[ebp]
        cdq
        idiv    DWORD PTR _j$[ebp]
        test    edx, edx

    [download]

Now let's look at the assembler that sits behind that perl modulo instruction: 

PUBLIC    _Perl_pp_modulo
PUBLIC    __real@41f0000000000000
PUBLIC    __real@3fe0000000000000
EXTRN    _fmod:NEAR
EXTRN    _floor:NEAR
EXTRN    _Perl_cast_uv:NEAR
;    COMDAT __real@41f0000000000000
CONST    SEGMENT
__real@41f0000000000000 DQ 041f0000000000000r    ; 4.29497e+009
CONST    ENDS
;    COMDAT __real@3fe0000000000000
CONST    SEGMENT
__real@3fe0000000000000 DQ 03fe0000000000000r    ; 0.5
; Function compile flags: /Ods
CONST    ENDS
_TEXT    SEGMENT
tv555 = -128
tv526 = -120
tv272 = -112
tv270 = -108
tv232 = -100
tv206 = -96
tv204 = -92
tv171 = -84
tv75 = -80
_ans$32800 = -76
_dans$32794 = -72
_aiv$32779 = -64
_biv$32756 = -60
_dright$32743 = -56
_right_neg$32740 = -45
_right$32738 = -44
_left$32737 = -40
_dright_valid$32742 = -35
_left_neg$32739 = -34
_use_double$32741 = -33
_dleft$32744 = -32
_right$32719 = -20
_left$32720 = -16
_tmpsv$32718 = -12
_targ$ = -8
_sp$ = -4
_my_perl$ = 8
_Perl_pp_modulo PROC NEAR
; Line 1260
    push    ebp
    mov    ebp, esp
    sub    esp, 128                ; 00000080H
; Line 1261
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    DWORD PTR _sp$[ebp], eax
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    eax, DWORD PTR [eax+4]
    movzx    eax, BYTE PTR [eax+20]
    and    eax, 64                    ; 00000040H
    test    eax, eax
    je    SHORT $L37477
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax-4]
    mov    DWORD PTR tv75[ebp], eax
    jmp    SHORT $L37478
$L37477:
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    eax, DWORD PTR [eax+4]
    mov    eax, DWORD PTR [eax+12]
    mov    ecx, DWORD PTR _my_perl$[ebp]
    mov    ecx, DWORD PTR [ecx+8]
    mov    eax, DWORD PTR [ecx+eax*4]
    mov    DWORD PTR tv75[ebp], eax
$L37478:
    mov    eax, DWORD PTR tv75[ebp]
    mov    DWORD PTR _targ$[ebp], eax
$L32714:
    mov    eax, DWORD PTR _my_perl$[ebp]
    cmp    DWORD PTR [eax+2624], 0
    je    $L32715
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    DWORD PTR _right$32719[ebp], eax
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax-4]
    mov    DWORD PTR _left$32720[ebp], eax
    mov    eax, DWORD PTR _left$32720[ebp]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 268435456                ; 10000000H
    test    eax, eax
    jne    SHORT $L32722
    mov    eax, DWORD PTR _right$32719[ebp]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 268435456                ; 10000000H
    test    eax, eax
    je    $L32715
$L32722:
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    eax, DWORD PTR [eax+4]
    movzx    eax, BYTE PTR [eax+20]
    and    eax, 64                    ; 00000040H
    neg    eax
    sbb    eax, eax
    and    eax, 4
    push    eax
    push    14                    ; 0000000eH
    push    DWORD PTR _right$32719[ebp]
    push    DWORD PTR _left$32720[ebp]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_amagic_call
    add    esp, 20                    ; 00000014H
    mov    DWORD PTR _tmpsv$32718[ebp], eax
    cmp    DWORD PTR _tmpsv$32718[ebp], 0
    je    $L32715
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    DWORD PTR _sp$[ebp], eax
    mov    eax, DWORD PTR _sp$[ebp]
    sub    eax, 4
    mov    DWORD PTR _sp$[ebp], eax
$L32724:
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    eax, DWORD PTR [eax+4]
    movzx    eax, BYTE PTR [eax+20]
    and    eax, 64                    ; 00000040H
    test    eax, eax
    jne    SHORT $L32728
    mov    eax, DWORD PTR _targ$[ebp]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 1024                ; 00000400H
    test    eax, eax
    je    SHORT $L32727
$L32728:
    push    2
    push    DWORD PTR _tmpsv$32718[ebp]
    push    DWORD PTR _targ$[ebp]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_sv_setsv_flags
    add    esp, 16                    ; 00000010H
$L32732:
    mov    eax, DWORD PTR _targ$[ebp]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 16384                ; 00004000H
    test    eax, eax
    je    SHORT $L32733
    push    DWORD PTR _targ$[ebp]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_mg_set
    pop    ecx
    pop    ecx
$L32733:
    xor    eax, eax
    test    eax, eax
    jne    SHORT $L32732
    mov    eax, DWORD PTR _sp$[ebp]
    mov    ecx, DWORD PTR _targ$[ebp]
    mov    DWORD PTR [eax], ecx
    xor    eax, eax
    test    eax, eax
    jne    SHORT $L32732
    jmp    SHORT $L32725
$L32727:
    mov    eax, DWORD PTR _sp$[ebp]
    mov    ecx, DWORD PTR _tmpsv$32718[ebp]
    mov    DWORD PTR [eax], ecx
$L32725:
    xor    eax, eax
    test    eax, eax
    jne    SHORT $L32724
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    ecx, DWORD PTR _sp$[ebp]
    mov    DWORD PTR [eax], ecx
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    eax, DWORD PTR [eax+4]
    mov    eax, DWORD PTR [eax]
    jmp    $L32711
$L32715:
    xor    eax, eax
    test    eax, eax
    jne    $L32714
; Line 1263
    and    DWORD PTR _left$32737[ebp], 0
; Line 1264
    and    DWORD PTR _right$32738[ebp], 0
; Line 1265
    and    BYTE PTR _left_neg$32739[ebp], 0
; Line 1266
    and    BYTE PTR _right_neg$32740[ebp], 0
; Line 1267
    and    BYTE PTR _use_double$32741[ebp], 0
; Line 1268
    and    BYTE PTR _dright_valid$32742[ebp], 0
; Line 1269
    fldz
    fstp    QWORD PTR _dright$32743[ebp]
; Line 1270
    fldz
    fstp    QWORD PTR _dleft$32744[ebp]
$L32745:
; Line 1272
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 16777216                ; 01000000H
    test    eax, eax
    jne    SHORT $L32746
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 131072                ; 00020000H
    test    eax, eax
    jne    SHORT $L32749
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 262144                ; 00040000H
    test    eax, eax
    je    SHORT $L32746
$L32749:
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 65536                ; 00010000H
    test    eax, eax
    je    SHORT $L37479
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+12]
    mov    DWORD PTR tv171[ebp], eax
    jmp    SHORT $L32746
$L37479:
    mov    eax, DWORD PTR _sp$[ebp]
    push    DWORD PTR [eax]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_sv_2iv
    pop    ecx
    pop    ecx
    mov    DWORD PTR tv171[ebp], eax
$L32746:
    xor    eax, eax
    test    eax, eax
    jne    SHORT $L32745
; Line 1273
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 65536                ; 00010000H
    test    eax, eax
    je    SHORT $L32752
; Line 1274
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+8]
    and    eax, -2147418112            ; 80010000H
    xor    ecx, ecx
    cmp    eax, -2147418112            ; 80010000H
    setne    cl
    mov    BYTE PTR _right_neg$32740[ebp], cl
; Line 1275
    movsx    eax, BYTE PTR _right_neg$32740[ebp]
    test    eax, eax
    jne    SHORT $L32753
; Line 1276
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+12]
    mov    DWORD PTR _right$32738[ebp], eax
    mov    eax, DWORD PTR _sp$[ebp]
    sub    eax, 4
    mov    DWORD PTR _sp$[ebp], eax
; Line 1277
    jmp    SHORT $L32755
$L32753:
; Line 1278
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+12]
    mov    DWORD PTR _biv$32756[ebp], eax
    mov    eax, DWORD PTR _sp$[ebp]
    sub    eax, 4
    mov    DWORD PTR _sp$[ebp], eax
; Line 1279
    cmp    DWORD PTR _biv$32756[ebp], 0
    jl    SHORT $L32758
; Line 1280
    mov    eax, DWORD PTR _biv$32756[ebp]
    mov    DWORD PTR _right$32738[ebp], eax
; Line 1281
    and    BYTE PTR _right_neg$32740[ebp], 0
; Line 1282
    jmp    SHORT $L32755
$L32758:
; Line 1283
    mov    eax, DWORD PTR _biv$32756[ebp]
    neg    eax
    mov    DWORD PTR _right$32738[ebp], eax
$L32755:
; Line 1287
    jmp    $L32767
$L32752:
; Line 1288
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    ecx, DWORD PTR _sp$[ebp]
    mov    ecx, DWORD PTR [ecx]
    mov    DWORD PTR [eax+84], ecx
    mov    eax, DWORD PTR _sp$[ebp]
    sub    eax, 4
    mov    DWORD PTR _sp$[ebp], eax
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    eax, DWORD PTR [eax+84]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 131072                ; 00020000H
    test    eax, eax
    je    SHORT $L37481
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    eax, DWORD PTR [eax+84]
    mov    eax, DWORD PTR [eax]
    fld    QWORD PTR [eax+16]
    fstp    QWORD PTR tv204[ebp]
    jmp    SHORT $L37482
$L37481:
    mov    eax, DWORD PTR _my_perl$[ebp]
    push    DWORD PTR [eax+84]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_sv_2nv
    pop    ecx
    pop    ecx
    fstp    QWORD PTR tv204[ebp]
$L37482:
    fld    QWORD PTR tv204[ebp]
    fst    QWORD PTR _dright$32743[ebp]
; Line 1289
    fcomp    QWORD PTR __real@0000000000000000
    fnstsw    ax
    test    ah, 5
    jp    SHORT $L37483
    mov    DWORD PTR tv206[ebp], 1
    jmp    SHORT $L37484
$L37483:
    and    DWORD PTR tv206[ebp], 0
$L37484:
    mov    al, BYTE PTR tv206[ebp]
    mov    BYTE PTR _right_neg$32740[ebp], al
; Line 1290
    movsx    eax, BYTE PTR _right_neg$32740[ebp]
    test    eax, eax
    je    SHORT $L32762
; Line 1291
    fld    QWORD PTR _dright$32743[ebp]
    fchs
    fstp    QWORD PTR _dright$32743[ebp]
$L32762:
; Line 1292
    fld    QWORD PTR _dright$32743[ebp]
    fcomp    QWORD PTR __real@41f0000000000000
    fnstsw    ax
    test    ah, 5
    jp    SHORT $L32764
; Line 1293
    fld    QWORD PTR _dright$32743[ebp]
    push    ecx
    push    ecx
    fstp    QWORD PTR [esp]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_cast_uv
    add    esp, 12                    ; 0000000cH
    mov    DWORD PTR _right$32738[ebp], eax
; Line 1294
    mov    BYTE PTR _dright_valid$32742[ebp], 1
; Line 1295
    jmp    SHORT $L32767
$L32764:
; Line 1296
    mov    BYTE PTR _use_double$32741[ebp], 1
$L32767:
; Line 1303
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 16777216                ; 01000000H
    test    eax, eax
    jne    SHORT $L32768
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 131072                ; 00020000H
    test    eax, eax
    jne    SHORT $L32771
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 262144                ; 00040000H
    test    eax, eax
    je    SHORT $L32768
$L32771:
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 65536                ; 00010000H
    test    eax, eax
    je    SHORT $L37485
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+12]
    mov    DWORD PTR tv232[ebp], eax
    jmp    SHORT $L32768
$L37485:
    mov    eax, DWORD PTR _sp$[ebp]
    push    DWORD PTR [eax]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_sv_2iv
    pop    ecx
    pop    ecx
    mov    DWORD PTR tv232[ebp], eax
$L32768:
    xor    eax, eax
    test    eax, eax
    jne    SHORT $L32767
; Line 1304
    movsx    eax, BYTE PTR _use_double$32741[ebp]
    test    eax, eax
    jne    $L32774
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 65536                ; 00010000H
    test    eax, eax
    je    $L32774
; Line 1305
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 65536                ; 00010000H
    test    eax, eax
    je    SHORT $L32775
; Line 1306
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+8]
    and    eax, -2147418112            ; 80010000H
    xor    ecx, ecx
    cmp    eax, -2147418112            ; 80010000H
    setne    cl
    mov    BYTE PTR _left_neg$32739[ebp], cl
; Line 1307
    movsx    eax, BYTE PTR _left_neg$32739[ebp]
    test    eax, eax
    jne    SHORT $L32776
; Line 1308
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+12]
    mov    DWORD PTR _left$32737[ebp], eax
    mov    eax, DWORD PTR _sp$[ebp]
    sub    eax, 4
    mov    DWORD PTR _sp$[ebp], eax
; Line 1309
    jmp    SHORT $L32775
$L32776:
; Line 1310
    mov    eax, DWORD PTR _sp$[ebp]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax]
    mov    eax, DWORD PTR [eax+12]
    mov    DWORD PTR _aiv$32779[ebp], eax
    mov    eax, DWORD PTR _sp$[ebp]
    sub    eax, 4
    mov    DWORD PTR _sp$[ebp], eax
; Line 1311
    cmp    DWORD PTR _aiv$32779[ebp], 0
    jl    SHORT $L32781
; Line 1312
    mov    eax, DWORD PTR _aiv$32779[ebp]
    mov    DWORD PTR _left$32737[ebp], eax
; Line 1313
    and    BYTE PTR _left_neg$32739[ebp], 0
; Line 1314
    jmp    SHORT $L32775
$L32781:
; Line 1315
    mov    eax, DWORD PTR _aiv$32779[ebp]
    neg    eax
    mov    DWORD PTR _left$32737[ebp], eax
$L32775:
; Line 1320
    jmp    $L32783
$L32774:
; Line 1321
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    ecx, DWORD PTR _sp$[ebp]
    mov    ecx, DWORD PTR [ecx]
    mov    DWORD PTR [eax+84], ecx
    mov    eax, DWORD PTR _sp$[ebp]
    sub    eax, 4
    mov    DWORD PTR _sp$[ebp], eax
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    eax, DWORD PTR [eax+84]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 131072                ; 00020000H
    test    eax, eax
    je    SHORT $L37487
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    eax, DWORD PTR [eax+84]
    mov    eax, DWORD PTR [eax]
    fld    QWORD PTR [eax+16]
    fstp    QWORD PTR tv270[ebp]
    jmp    SHORT $L37488
$L37487:
    mov    eax, DWORD PTR _my_perl$[ebp]
    push    DWORD PTR [eax+84]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_sv_2nv
    pop    ecx
    pop    ecx
    fstp    QWORD PTR tv270[ebp]
$L37488:
    fld    QWORD PTR tv270[ebp]
    fst    QWORD PTR _dleft$32744[ebp]
; Line 1322
    fcomp    QWORD PTR __real@0000000000000000
    fnstsw    ax
    test    ah, 5
    jp    SHORT $L37489
    mov    DWORD PTR tv272[ebp], 1
    jmp    SHORT $L37490
$L37489:
    and    DWORD PTR tv272[ebp], 0
$L37490:
    mov    al, BYTE PTR tv272[ebp]
    mov    BYTE PTR _left_neg$32739[ebp], al
; Line 1323
    movsx    eax, BYTE PTR _left_neg$32739[ebp]
    test    eax, eax
    je    SHORT $L32785
; Line 1324
    fld    QWORD PTR _dleft$32744[ebp]
    fchs
    fstp    QWORD PTR _dleft$32744[ebp]
$L32785:
; Line 1328
    movsx    eax, BYTE PTR _use_double$32741[ebp]
    test    eax, eax
    jne    SHORT $L32783
; Line 1329
    fld    QWORD PTR _dleft$32744[ebp]
    fcomp    QWORD PTR __real@41f0000000000000
    fnstsw    ax
    test    ah, 5
    jp    SHORT $L32788
; Line 1332
    fld    QWORD PTR _dleft$32744[ebp]
    push    ecx
    push    ecx
    fstp    QWORD PTR [esp]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_cast_uv
    add    esp, 12                    ; 0000000cH
    mov    DWORD PTR _left$32737[ebp], eax
; Line 1336
    jmp    SHORT $L32783
$L32788:
; Line 1340
    fld    QWORD PTR _dleft$32744[ebp]
    fadd    QWORD PTR __real@3fe0000000000000
    push    ecx
    push    ecx
    fstp    QWORD PTR [esp]
    call    _floor
    pop    ecx
    pop    ecx
    fstp    QWORD PTR _dleft$32744[ebp]
; Line 1341
    mov    BYTE PTR _use_double$32741[ebp], 1
; Line 1342
    movsx    eax, BYTE PTR _dright_valid$32742[ebp]
    test    eax, eax
    je    SHORT $L32791
; Line 1343
    fld    QWORD PTR _dright$32743[ebp]
    fadd    QWORD PTR __real@3fe0000000000000
    push    ecx
    push    ecx
    fstp    QWORD PTR [esp]
    call    _floor
    pop    ecx
    pop    ecx
    fstp    QWORD PTR _dright$32743[ebp]
; Line 1344
    jmp    SHORT $L32783
$L32791:
; Line 1345
    mov    eax, DWORD PTR _right$32738[ebp]
    mov    DWORD PTR tv526[ebp], eax
    and    DWORD PTR tv526[ebp+4], 0
    fild    QWORD PTR tv526[ebp]
    fstp    QWORD PTR _dright$32743[ebp]
$L32783:
; Line 1349
    movsx    eax, BYTE PTR _use_double$32741[ebp]
    test    eax, eax
    je    $L32793
; Line 1352
    fld    QWORD PTR _dright$32743[ebp]
    fcomp    QWORD PTR __real@0000000000000000
    fnstsw    ax
    test    ah, 68                    ; 00000044H
    jp    SHORT $L32795
; Line 1353
    push    OFFSET FLAT:$SG32796
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_die
    pop    ecx
    pop    ecx
    jmp    $L32711
$L32795:
; Line 1355
    fld    QWORD PTR _dright$32743[ebp]
    push    ecx
    push    ecx
    fstp    QWORD PTR [esp]
    fld    QWORD PTR _dleft$32744[ebp]
    push    ecx
    push    ecx
    fstp    QWORD PTR [esp]
    call    _fmod
    add    esp, 16                    ; 00000010H
    fstp    QWORD PTR _dans$32794[ebp]
; Line 1356
    movsx    eax, BYTE PTR _left_neg$32739[ebp]
    movsx    ecx, BYTE PTR _right_neg$32740[ebp]
    cmp    eax, ecx
    je    SHORT $L32797
    fld    QWORD PTR _dans$32794[ebp]
    fcomp    QWORD PTR __real@0000000000000000
    fnstsw    ax
    test    ah, 68                    ; 00000044H
    jnp    SHORT $L32797
; Line 1357
    fld    QWORD PTR _dright$32743[ebp]
    fsub    QWORD PTR _dans$32794[ebp]
    fstp    QWORD PTR _dans$32794[ebp]
$L32797:
; Line 1358
    movsx    eax, BYTE PTR _right_neg$32740[ebp]
    test    eax, eax
    je    SHORT $L32798
; Line 1359
    fld    QWORD PTR _dans$32794[ebp]
    fchs
    fstp    QWORD PTR _dans$32794[ebp]
$L32798:
; Line 1360
    fld    QWORD PTR _dans$32794[ebp]
    push    ecx
    push    ecx
    fstp    QWORD PTR [esp]
    push    DWORD PTR _targ$[ebp]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_sv_setnv
    add    esp, 16                    ; 00000010H
; Line 1362
    jmp    $L32814
$L32793:
; Line 1365
    cmp    DWORD PTR _right$32738[ebp], 0
    jne    SHORT $L32801
; Line 1366
    push    OFFSET FLAT:$SG32802
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_die
    pop    ecx
    pop    ecx
    jmp    $L32711
$L32801:
; Line 1368
    mov    eax, DWORD PTR _left$32737[ebp]
    xor    edx, edx
    div    DWORD PTR _right$32738[ebp]
    mov    DWORD PTR _ans$32800[ebp], edx
; Line 1369
    movsx    eax, BYTE PTR _left_neg$32739[ebp]
    movsx    ecx, BYTE PTR _right_neg$32740[ebp]
    cmp    eax, ecx
    je    SHORT $L32803
    cmp    DWORD PTR _ans$32800[ebp], 0
    je    SHORT $L32803
; Line 1370
    mov    eax, DWORD PTR _right$32738[ebp]
    sub    eax, DWORD PTR _ans$32800[ebp]
    mov    DWORD PTR _ans$32800[ebp], eax
$L32803:
; Line 1371
    movsx    eax, BYTE PTR _right_neg$32740[ebp]
    test    eax, eax
    je    SHORT $L32804
; Line 1374
    cmp    DWORD PTR _ans$32800[ebp], -2147483647    ; 80000001H
    ja    SHORT $L32807
; Line 1375
    mov    eax, DWORD PTR _ans$32800[ebp]
    not    eax
    inc    eax
    push    eax
    push    DWORD PTR _targ$[ebp]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_sv_setiv
    add    esp, 12                    ; 0000000cH
; Line 1376
    jmp    SHORT $L32808
$L32807:
; Line 1377
    mov    eax, DWORD PTR _ans$32800[ebp]
    mov    DWORD PTR tv555[ebp], eax
    and    DWORD PTR tv555[ebp+4], 0
    fild    QWORD PTR tv555[ebp]
    fchs
    push    ecx
    push    ecx
    fstp    QWORD PTR [esp]
    push    DWORD PTR _targ$[ebp]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_sv_setnv
    add    esp, 16                    ; 00000010H
$L32808:
; Line 1379
    jmp    SHORT $L32814
$L32804:
; Line 1380
    push    DWORD PTR _ans$32800[ebp]
    push    DWORD PTR _targ$[ebp]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_sv_setuv
    add    esp, 12                    ; 0000000cH
$L32814:
; Line 1382
    mov    eax, DWORD PTR _targ$[ebp]
    mov    eax, DWORD PTR [eax+8]
    and    eax, 16384                ; 00004000H
    test    eax, eax
    je    SHORT $L32815
    push    DWORD PTR _targ$[ebp]
    push    DWORD PTR _my_perl$[ebp]
    call    _Perl_mg_set
    pop    ecx
    pop    ecx
$L32815:
    xor    eax, eax
    test    eax, eax
    jne    SHORT $L32814
    mov    eax, DWORD PTR _sp$[ebp]
    add    eax, 4
    mov    DWORD PTR _sp$[ebp], eax
    mov    eax, DWORD PTR _sp$[ebp]
    mov    ecx, DWORD PTR _targ$[ebp]
    mov    DWORD PTR [eax], ecx
    xor    eax, eax
    test    eax, eax
    jne    SHORT $L32814
; Line 1383
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    ecx, DWORD PTR _sp$[ebp]
    mov    DWORD PTR [eax], ecx
    mov    eax, DWORD PTR _my_perl$[ebp]
    mov    eax, DWORD PTR [eax+4]
    mov    eax, DWORD PTR [eax]
$L32711:
; Line 1385
    leave
    ret    0
_Perl_pp_modulo ENDP
_TEXT    ENDS

[download]

So the answer to your question is: when you understand why those four instructions in the C version, require those 700+ lines of assembler for the perl version, then you'll understand why the performance difference exists.

And also why it isn't a problem!

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

In Section Seekers of Perl Wisdom