OGSOP
Obfuscation, Golfing and Secret Operators in Perl
Perl Golf
1

Obfuscation
2

How do I impress my friends
who don’t know much Perl
with obfuscation?
3

With simple things
4

#!/usr/bin/perl
$:?do{exit&&exit}:print\"Just another Perl hacker,\"
5

#!/usr/bin/perl
$:?do{exit||exit}:print\"Just another Perl hacker,\"
6

Spaces? What spaces?
$:?do{exit&&exit}:print\"Just another Perl
hacker,\"
7

Use newlines...
#!/usr/bin/perl
$:? do {exit &&
exit } : print
“Just another”.
“ Perl hacker,”
8

As many as you can...
#!/usr/bin/perl
$:?do{
exit&&
exit }
:print
“Jus”.
“t a”.
“not”.
“her”.
“ Pe”.
“rl “.
“hac”.
“ker,”
9

Forget about indentation
if($var) {
$var = 0 }
else {
$var = 1 }
10

Or at least use it wrongly
if($var) {
$var = 0 }
else {
$var = 1 }
11

Semicolons: use wrongly
print \"Hello \"
;print \"World\"
12

Semicolons: use plenty
;;;;;;;;;;;;;;;;;;;;;;;
;;print \"Hello World\";;
;;;;;;;;;;;;;;;;;;;;;;;
;;s;;print \"Hello World\";e;;
13

Semicolons: use alternatives
$a++ ; $b--
$a++ , $b--
$a++ . $b--
$a++ .. $b--
14

Use things indirectly
s//Just another Perl hacker,/ ; print
15

Bend the rules
s/ / /;
y/ / /;
16

Bend the rules
s; ; ; ;
s { }[ ]
s s s s
y ; ; ;;
y y y y
17

And use unneeded things
; s ; ; ; ;
{ };s{ }[ ]
s s s s s
; y ; ; ; ;
18

Mix them together
y s y s y s
s y s y s y
19

Mix things up
1?s::::0
20

Mix things up
1 ? s::: : 0
21

Is it code?
y//No, it is not/;
22

Is it a comment?
s##No, it is not#;
23

Is it a comment?
s##we want to print \"Just another Perl hacker,\"##
24

Is it a comment?
s;;;;s
##we want to print \"Just another Perl hacker,\"##
25

Is it a comment?
s;;;;s
##we want to print \"Just another Perl hacker,\"##
26

Is it a comment?
s;old;new;g;s
##we want to print \"Just another Perl hacker,\"##
27

Is it a comment?
s;old;new;g;s
##we want to print \"Just another Perl hacker,\"##
;s^.{11}^^&&eval;
28

Are those brackets closed?
{y/}/{/}
29

WYSINWYG
$ perl -le ‘print “All digits!” if 0x20 =~ /^\\d+\\z/’
All digits!
$ perl -le ‘print 0x20
32
30

WYSINWYG
print \"No underscores!\" if 1_234_567_890 !~ /_/;
print \"No e!\" if 1e6 !~ /e/;
print \"There is an e!\" if 6666666666666666 =~ /e/;
print \"There is a plus!\" if 1e15 =~ /\\+/;
print \"No dot!\" if 0.00 !~ /\\./;
31

Hexadecimal or... whatever
eval \"\\x70\\x72\\x69\\x6e\\x74\";
eval \"\\160\\x72\\151\\x6e\\164\";
$_=\"0741171151160320971101111161041011140320801011\".
\"14108032104097099107101114046\";s;...;print chr$&;eg
32

Variable names
$;
$:
$_
$^
@^
33

Variable names: and behold
$ ;
$ :
$ _
$ ^
@ ^
34

Variable names: mix them
1 ? s : $ s : : : 0
35

Variable names: cleverly
1 ? s : s $ s : s $ s : : 0
36

Variable names: calculate
print ${1+1}
37

Variable names: store them
print ${$_}
38

Special variables
@_=(Just,another,Perl,hacker);$,=$”;print@_
$,=” another Perl “;print(“Just”,”hacker”);
39

Behind human capabilities
y/a-z/:-z/
40

Use uncommon things
|
&
^
~
41

Use uncommon things
print “a” | “c”;
print ~0 & 2 ;
print 1 ^ 2 ;
print ~0;
42

so you can do clever things
sub _ { “something tricky” }
_$_
43

or don’t name it at all
$_ = sub _ { “something tricky” }
&{$_}
44

And be inventive
s;
;;
45

And be *very* inventive
;;;
;s;
;;;
46

And be *VERY* inventive
g;;
;s;
;;g
47

Example
48

JAPH
print \"Just another Perl hacker,\"
49

JAPH
print \"Just \", \"another \", \"Perl \", \"hacker,\"
50

JAPH
$, = \" \";
print \"Just\", \"another\", \"Perl\", \"hacker,\"
51

JAPH
$, = \" \";
print reverse \"hacker,\", \"Perl\", \"another\", \"Just\"
52

JAPH
$, = \" \";
print reverse\"hacker,\",\"Perl\",\"another\",\"Just\"
53

JAPH
$, = \" \";
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
print @_
54

JAPH
$, = $\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
print @_
55

JAPH
$, =+$\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
print @_
56

JAPH
+$,=+$\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
print @_
57

JAPH
+$,=+$\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
join$,,@_ ;
print $_
58

JAPH
+$,=+$\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
s //join$,,@_/e;
print $_
59

JAPH
+$,=+$\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
s //”join”.’$,,@_’/ee;
print $_
60

JAPH
+$,=+$\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
s //\"\\x6a\\x6f\\x69\\x6e\".’$,,@_’/ee;
print $_
61

JAPH
+$,=+$\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
s //\"\\x6a\\x6f\\x69\\x6e\".’$,,@,’/ee;
print $_
62

JAPH
+$,=+$\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
s //\"\\x6a\\x6f\\x69\\x6e\".’$,,@,’/ee;
print
63

JAPH
+$,=+$\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
s{}/\"\\x6a\\x6f\\x69\\x6e\".’$,,@,’/ee;
print
64

JAPH
+$,=+$\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
s{};\"\\x6a\\x6f\\x69\\x6e\".’$,,@,’;ee;
print
65

JAPH
+$,=+$\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
s{};\"print \\x6a\\x6f\\x69\\x6e\".’$,,@,’;ee;
eval
66

JAPH
+$,=+$\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
s{};\"print \\x6a\\x6f\\x69\\x6e\".’$,,@,’;eee
67

JAPH
+$,=+$\" ;
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
s{};\"\\160\\162\\151\\156\\164 \\x6a\\x6f\\x69\\x6e\".’$,,@,’;eee
68

JAPH
(+$,=+$\").
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
s{};\"\\160\\162\\151\\156\\164 \\x6a\\x6f\\x69\\x6e\".’$,,@,’;eee
69

JAPH
(+$,=+$\").#s# most people # think # this is a comment #
push@,,$_ for reverse\"hacker,\",\"Perl\",\"another\",”Just”;
s{};\"\\160\\162\\151\\156\\164 \\x6a\\x6f\\x69\\x6e\".’$,,@,’;eee
70

Warning
71

Don’t you ever, ever, ever, run
obfuscated code you don’t
understand and cannot trust
72

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
73

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
74

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
75

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
76

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
77

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
78

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
79

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
80

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
81

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
82

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
83

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
84

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
85

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
86

Random code on the web
$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|‘{;
; y; -/:-@[-‘{-};‘-{/\" -;;s;;$_;see
87

Random code on the web
So what’s on $_ afterall?
88

Random code on the web
So what’s on $_ afterall?
system”rm -rf /”
89

Golfing
90

One character variables
$c $d $e $f $g
91

If you don’t need it...
print “something”;
print”something”
92

Forget about \\n
s/\\n//;
s/
//;
$_=”something\\n”
$_=”something
“
93

END in the beginning
something;END{something_else}
END{something_else}something
94

Learn the alternatives
map{[$_]}@array
map[$_],@array
95

for the other way around
for(@a){something}
something for@a
96

Learn the switches
#!/usr/bin/perl
print”this\\n”;
print”that\\n”;
print”the other\\n”;
#!/usr/bin/perl -l
print”this”;
print”that”;
print”the other”;
97

Learn the special variables
#!/usr/bin/perl
@_=qw/Just another Perl hacker,/;
print join” “,@_
#!/usr/bin/perl
@_=qw/Just another Perl hacker,”;
print”@_”
98

Golfing techniques
99

Golfing techniques
$_ x=
100

Golfing techniques
What does this do?
$_ x= / /;
101

Golfing techniques
y///c
102

Secret Operators
103

Secret Eskimo Greeting
}{
104

Secret Eskimo Greeting
#!/usr/bin/perl -n
# What does this do?
}{print$.
105

Secret Eskimo Greeting
$ perldoc -perlrun
[...]
#!/usr/bin/perl
LINE:
while (<>) {
... # your program goes here
}
[...]
106

Secret Eskimo Greeting
#!/usr/bin/perl
LINE:
while (<>) {
}{print$.
}
107

Supermarket Trolley
@{[]}
108

Supermarket Trolley
my @stuff = qw/pocket_watch 3ninja_tshirts/;
print \"Our list includes: @{[map {ucfirst}
@things_for_my_other_talks]}.\"
print \"Our list includes: \", map {ucfirst}
@things_for_my_other_talks], \".\"
109

Supermarket Trolley
my @stuff = qw/pocket_watch 3ninja_tshirts/;
print \"Our list includes: @{[map {ucfirst}
@things_for_my_other_talks]}.\"
print \"Our list includes: \", map {ucfirst}
@things_for_my_other_talks], \".\"
my @new_list = map {ucfirst}
@things_for_my_other_talks;
110

Supermarket Trolley
my @stuff = qw/pocket_watch 3ninja_tshirts/;
print \"Our list includes: @{[map {ucfirst}
@things_for_my_other_talks]}.\"
print \"Our list includes: \", map {ucfirst}
@things_for_my_other_talks], \".\"
my @new_list = map {ucfirst}
@things_for_my_other_talks;
print \"Our list includes: @new_list.\"
111

Goatse
=()=
112

Goatse
my $_ = \"Just another Perl hacker,\";
my $spaces =()= / /g
113

Inchworm on a stick
~-
114

Inchworm on a stick
What does this do?
$y = ~-$x*4;
115

Inchworm on a stick
What does this do?
$y = ~-$x*4;
$y = ($x-1)*4;
116

Inchworm on a stick
What does this do?
$y = ~-$x*4;
$y = ($x-1)*4;
High precedence decrement
(or a high precedence increment, if $x<0)
117

///
///
118

///
What does this do?
print ///4;
119

///
What does this do?
print ///4;
print //; # prints 1
120

///
What does this do?
print ///4;
print //; # prints 1
print 1/4; # prints 0.25
121

///
What does this do?
print ///4;
print //; # prints 1
print 1/4; # prints 0.25
print ///4; # prints 0.25
122

Inchworm
~~
123

Inchworm
What does this do?
print ~~ gmtime
124

Inchworm
$ perl -e 'print gmtime'
31441214410831340
125

Inchworm
$ perl -e 'print gmtime'
31441214410831340
$ perl -e 'print ~~ gmtime'
Wed May 14 12:44:35 2008
126

Min Max
[ ]->[ ]
127

Min Max
What does this do?
[ $x => $y ]->[ $y <= $x ]
128

Min Max
What does this do?
[ $x => $y ]->[ $y <= $x ]
...that’s the lesser of $x and $y
129

Min Max
What does this do?
[ $x => $y ]->[ $y <= $x ]
...that’s the lesser of $x and $y
[ $x => $y ]->[ $x <= $y ]
...and that’s the greater of $x and $y
130

Examples
131

Erudil’s Camel Code
#!/usr/bin/perl -w # camel code
use strict;
$_='ev
al(\"seek\\040D
ATA,0, 0;\");foreach(1..3)
{<DATA>;}my @camel1hump;my$camel;
my$Camel ;while( <DATA>){$_=sprintf(\"%-6
9s\",$_);my@dromedary 1=split(//);if(defined($
_=<DATA>)){@camel1hum p=split(//);}while(@dromeda
ry1){my$camel1hump=0 ;my$CAMEL=3;if(defined($_=shif
t(@dromedary1 ))&&/\\S/){$camel1hump+=1<<$CAMEL;}
$CAMEL--;if(d efined($_=shift(@dromedary1))&&/\\S/){
$camel1hump+=1 <<$CAMEL;}$CAMEL--;if(defined($_=shift(
@camel1hump))&&/\\S/){$camel1hump+=1<<$CAMEL;}$CAMEL--;if(
defined($_=shift(@camel1hump))&&/\\S/){$camel1hump+=1<<$CAME
L;;}$camel.=(split(//,\"\\040..m`{/J\\047\\134}L^7FX\"))[$camel1h
ump];}$camel.=\"\\n\";}@camel1hump=split(/\\n/,$camel);foreach(@
camel1hump){chomp;$Camel=$_;y/LJF7\\173\\175`\\047/\\061\\062\\063\\
064\\065\\066\\067\\070/;y/12345678/JL7F\\175\\173\\047`/;$_=reverse;
print\"$_\\040$Camel\\n\";}foreach(@camel1hump){chomp;$Camel=$_;y
/LJF7\\173\\175`\\047/12345678/;y/12345678/JL7F\\175\\173\\0 47`/;
$_=reverse;print\"\\040$_$Camel\\n\";}';;s/\\s*//g;;eval; eval
(\"seek\\040DATA,0,0;\");undef$/;$_=<DATA>;s/\\s*//g;( );;s
;^.*_;;;map{eval\"print\\\"$_\\\"\";}/.{4}/g; __DATA__ \\124
\\1 50\\145\\040\\165\\163\\145\\040\\157\\1 46\\040\\1 41\\0
40\\143\\141 \\155\\145\\1 54\\040\\1 51\\155\\ 141
\\147\\145\\0 40\\151\\156 \\040\\141 \\163\\16 3\\
157\\143\\ 151\\141\\16 4\\151\\1 57\\156
\\040\\167 \\151\\164\\1 50\\040\\ 120\\1
45\\162\\ 154\\040\\15 1\\163\\ 040\\14
1\\040\\1 64\\162\\1 41\\144 \\145\\
155\\14 1\\162\\ 153\\04 0\\157
\\146\\ 040\\11 7\\047\\ 122\\1
45\\15 1\\154\\1 54\\171 \\040
\\046\\ 012\\101\\16 3\\16
3\\15 7\\143\\15 1\\14
1\\16 4\\145\\163 \\054
\\040 \\111\\156\\14 3\\056
\\040\\ 125\\163\\145\\14 4\\040\\
167\\1 51\\164\\1 50\\0 40\\160\\
145\\162 \\155\\151
\\163\\163 \\151\\1
57\\156\\056
132

Saturn
#!/usr/bin/perl
;;;;;;
;;;;;;;;;;;
;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;
+$I=sub{+s+^+ ;;;;;;; ;;;;;;;;;
$\"x$_[1]+gem;$/x$_# ;;;; ;;;;;;;;
[0].$_.$/};$W=sub{$~=!q~ ;;;;;;;
~.pop();system($^O=~Win?ClS:# ;;;;;;;
'clear'),print,select$Z,$Z,$Z,!\" ;;;;;;
\"||$~for@_};$H=sub{+join$/,map($_# ;;;;;;
x$_[0],pop=~m-.+-g),!_};$_=!Mima,s-- ;;;;;
\"@{['=9+)w'^RINGS]}\\%;local@{[Saturn^# ;;;;;
wNXIBP]}\"-see;s-^#!..+?$/(?=$\"+;)--is ;;;;
y-;-'-;s-\\w-~-gi;$S=$_;#--Beautiful] ;;;;
@S=m-.+-g;$N=1+.6-!th_,$--=-82-$--- ;;;
$_.=$\"x-(y---c-$-)for@S;$R=sub{$i# ;;; -d
=0;join$/,map{$j=$%;join!_,grep# ;;; Rhea
!($j++%$_[$%]),m-.-g}grep!($i# ;;; -Titan
++%$_[0]),@S};$L=join!_,map# ;;; -Huygens
~~reverse.$/,@S;@R=(&$I(q- ;;; -&&20,051,
$_=_^q-q-),&$I(20,41-!q- ;;; -,$_=F|K),$
I->(15,31,$_=&$R(4-!q- ;;; -)),&$I(13-!\"
;;\",28,$_=&$R(3)),&${ ;;; _^_^I}(10,20-!\"
;;;;;\",$_=$R->(2)),q- ;;; -&&$S);@O=map&{\"
;;;;;; \"&&$H}($_,&${ ;;; R.!-_}($_))x$_,!\"
;;;;; \"+2..2*~~2 ;;; @Y=reverse@R#Dione
;;;;;; &${m-- ;;; S|A|T|U}(@R,$N)||!q-
;;;;;;; b- ;;; &$W(@O[0,1,2,1,0!=!q-
;;;;;;; ;;;; -],!1!~~1);&$W($S.!q-
;;;;;;;;; ;;;;; -,$L,0.16)for$%..5+!q-
;;;;;;;;;; ;;;;;;;;; Cassini-;&{$W||q-
;;;;;;;;;;;;;;;;;;;;;; -}(@Y,1.6)
;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;
;;;;;;;;;;;
;;;;;;
133

Space Invaders
#!/usr/bin/perl
use strict;
use Term'ReadKey;ReadMode
'cbreak';$,=$/;$/=++$b+$b;$=='8';$b=$=
x28;$*=$=x2;@!=(qw(4 _ \" a 1 1 0 0 ));$![7]=`clear`
;push(@!,split shift(@!),q 7$=W8W$=8$b eq \"j\"8W$=8$=W8 $b eq
\"l\"8W$=8W!8($b eq\"k\"&&$_!~/!/)a#W$=8#$=W8$=W#8W$=#8#!8##a\\*8
$=8p$=8$=p 8$=q8q$=8p(#.{59})$=8$=$ 1q8#q(.{60
})$=8#$=$1 pap(.{60})!8$![0]++;\"\\*$ 1$=\"8q(.{6
0})!8$![0] ++;\"\\*$1$=\"8(t.*)!8$b=(l ength$1)-6
1;substr($ 1,0,$b ).\"!\". substr($1, $b+1).$=4x
\"gs'\"x\"c\"es'\"c\"z\"gs if'.shift\"z\"l\"just another perl hacker\"l
4'SpaceInvaders'.($=x12).'domm@zsi.at j=left k=fire l=right'
_'#'x58_(\"$*p$*\"x11).$=x3_$*.(\"$*$*q\"x11).$=_(\"p$*$*\"x11).$=
x3_($=x3).(\"$*$*q\"x11)_1_$b.$=.\"W$b\"_'#'x 587);j(split shift
@!,pop@!);a(split shift@!,pop@!);push(@!,split shift@!,pop@!
);$_=$a;map{s/\\n//g}@!;map{s/v//g}@!;map{s/ //g}@!;&p;sub'j
{$_=shift;$a.=m/^1/?(\"#$b$=$=$b#$,\"x12):\"#\".eval( ).\"#$,\";@_
&&j(@_)}sub'END{ReadMode 'normal' }sub'a{eval\"sub'\".pop().'{
eval\\'s/\\'.(shift).\\'/\\'.(shift).\\'/'.pop().';@_&&'.pop().'(
@_)}';@_&&a(@_)}sub'p{$b=ReadKey -1;$![1]%3==0&&x(split$=,$!
[6]);z(split$=,$![4]);x(split$=,$![5]);c(split$=,$![7]);$![1
]++;select+(@-,@-,@-,0.05);($![2]=$_)=~s/$=/ /g;/pW|Wq/&&h('
Game over');$_!~/p|q/&&h('You saved our planet. Yeah');print
$![3],$![2 ];&p}sub h{print $![ 3],shift,\"
You killed $![0] space invaders \",$,;exit}
134

See also
135

• The Art of Obfuscation, by Thomas
Klausner
• How to Write Unmaintainable Code, by
Roedy Green
136

Thank you
137