<s>
In	O
computer	B-General_Concept
programming	I-General_Concept
,	O
leaning	B-Language
toothpick	I-Language
syndrome	I-Language
(	O
LTS	O
)	O
is	O
the	O
situation	O
in	O
which	O
a	O
quoted	O
expression	O
becomes	O
unreadable	O
because	O
it	O
contains	O
a	O
large	O
number	O
of	O
escape	B-Algorithm
characters	I-Algorithm
,	O
usually	O
backslashes	O
("\"	O
)	O
,	O
to	O
avoid	O
delimiter	O
collision	O
.	O
</s>
<s>
The	O
official	O
Perl	B-Language
documentation	O
introduced	O
the	O
term	O
to	O
wider	O
usage	O
;	O
there	O
,	O
the	O
phrase	O
is	O
used	O
to	O
describe	O
regular	B-Language
expressions	I-Language
that	O
match	O
Unix-style	O
paths	B-Application
,	O
in	O
which	O
the	O
elements	O
are	O
separated	O
by	O
slashes	O
/	O
.	O
</s>
<s>
The	O
slash	O
is	O
also	O
used	O
as	O
the	O
default	O
regular	B-Language
expression	I-Language
delimiter	O
,	O
so	O
to	O
be	O
used	O
literally	O
in	O
the	O
expression	O
,	O
it	O
must	O
be	O
escaped	O
with	O
a	O
backslash	O
\,	O
leading	O
to	O
frequent	O
escaped	O
slashes	O
represented	O
as	O
\/	O
.	O
</s>
<s>
A	O
similar	O
phenomenon	O
occurs	O
for	O
DOS/Windows	O
paths	O
,	O
where	O
the	O
backslash	O
is	O
used	O
as	O
a	O
path	O
separator	O
,	O
requiring	O
a	O
doubled	O
backslash	O
\\	O
–	O
this	O
can	O
then	O
be	O
re-escaped	O
for	O
a	O
regular	B-Language
expression	I-Language
inside	O
an	O
escaped	O
string	O
,	O
requiring	O
\\\\	O
to	O
match	O
a	O
single	O
backslash	O
.	O
</s>
<s>
In	O
extreme	O
cases	O
,	O
such	O
as	O
a	O
regular	B-Language
expression	I-Language
in	O
an	O
escaped	O
string	O
,	O
matching	O
a	O
Uniform	O
Naming	O
Convention	O
path	O
(	O
which	O
begins	O
\\	O
)	O
requires	O
8	O
backslashes	O
\\\\\\\\	O
due	O
to	O
2	O
backslashes	O
each	O
being	O
double-escaped	O
.	O
</s>
<s>
LTS	O
appears	O
in	O
many	O
programming	O
languages	O
and	O
in	O
many	O
situations	O
,	O
including	O
in	O
patterns	O
that	O
match	O
Uniform	B-Protocol
Resource	I-Protocol
Identifiers	I-Protocol
(	O
URIs	B-Protocol
)	O
and	O
in	O
programs	O
that	O
output	O
quoted	O
text	O
.	O
</s>
<s>
Consider	O
the	O
following	O
Perl	B-Language
regular	B-Language
expression	I-Language
intended	O
to	O
match	O
URIs	B-Protocol
that	O
identify	O
files	O
under	O
the	O
pub	O
directory	O
of	O
an	O
FTP	B-Protocol
site	O
:	O
</s>
<s>
Perl	B-Language
,	O
like	O
sed	B-Application
before	O
it	O
,	O
solves	O
this	O
problem	O
by	O
allowing	O
many	O
other	O
characters	O
to	O
be	O
delimiters	O
for	O
a	O
regular	B-Language
expression	I-Language
.	O
</s>
<s>
A	O
Perl	B-Language
program	O
to	O
print	O
an	O
HTML	O
link	O
tag	O
,	O
where	O
the	O
URL	O
and	O
link	O
text	O
are	O
stored	O
in	O
variables	O
$url	O
and	O
$text	O
respectively	O
,	O
might	O
look	O
like	O
this	O
.	O
</s>
<s>
Using	O
single	O
quotes	O
to	O
delimit	O
the	O
string	O
is	O
not	O
feasible	O
,	O
as	O
Perl	B-Language
does	O
not	O
expand	O
variables	O
inside	O
single-quoted	O
strings	O
.	O
</s>
<s>
Using	O
the	O
printf	B-Language
function	O
is	O
a	O
viable	O
solution	O
in	O
many	O
languages	O
(	O
Perl	B-Language
,	O
C	B-Language
,	O
PHP	B-Application
)	O
:	O
</s>
<s>
The	O
qq	O
operator	O
in	O
Perl	B-Language
allows	O
for	O
any	O
delimiter	O
:	O
</s>
<s>
Here	O
documents	O
are	O
especially	O
well	O
suited	O
for	O
multi-line	O
strings	O
;	O
however	O
,	O
Perl	B-Language
here	O
documents	O
had	O
n't	O
allowed	O
for	O
proper	O
indentation	O
before	O
v5.26	O
.	O
</s>
<s>
This	O
example	O
shows	O
the	O
Perl	B-Language
syntax	O
:	O
</s>
<s>
The	O
C#	B-Application
programming	O
language	O
handles	O
LTS	O
by	O
the	O
use	O
of	O
the	O
@	O
symbol	O
at	O
the	O
start	O
of	O
string	B-Language
literals	I-Language
,	O
before	O
the	O
initial	O
quotation	O
marks	O
,	O
e.g.	O
</s>
<s>
The	O
C++11	B-Language
standard	O
adds	O
raw	O
strings	O
:	O
</s>
<s>
Go	B-Application
indicates	O
that	O
a	O
string	O
is	O
raw	O
by	O
using	O
the	O
backtick	O
as	O
a	O
delimiter	O
:	O
</s>
<s>
Python	B-Language
has	O
a	O
similar	O
construct	O
using	O
r	O
:	O
</s>
<s>
Ruby	B-Language
uses	O
single	O
quote	O
to	O
indicate	O
raw	O
string	O
:	O
</s>
<s>
It	O
also	O
has	O
regex	B-Language
percent	O
literals	O
with	O
choice	O
of	O
delimiter	O
like	O
Perl	B-Language
:	O
</s>
<s>
Scala	B-Application
allows	O
usage	O
of	O
triple	O
quotes	O
in	O
order	O
to	O
prevent	O
escaping	O
confusion	O
:	O
</s>
<s>
Sed	B-Application
regular	B-Language
expressions	I-Language
,	O
particularly	O
those	O
using	O
the	O
"	O
s	O
"	O
operator	O
,	O
are	O
much	O
similar	O
to	O
Perl	B-Language
(	O
sed	B-Application
is	O
a	O
predecessor	O
to	O
Perl	B-Language
)	O
.	O
</s>
