Perl Tutorial - 3: Escape Sequences Video Lecture | Perl Building Blocks: An Introduction to Perl - Back-End Programming

hello guys welcome to my channel this is
the third tutorial in this course and in
this we told we are going to talk about
escape sequences in Perl so an escape
sequence is a combination of characters
a slash and usually an alphabet that has
a special meaning input and escape
sequences are usually used to have
effects in displaying strings of text on
screen and for this tutorial we are
going to work with a file that's called
escaping underscore characters it has
the extension dot PL on line number 1 in
this file we have the shebang line and
then on line number 3 we have created a
variable called my underscore Val and if
you guys remember in Perl we create
variables using the dollar symbol so
there's the dollar symbol and the name
of the variable my underscore Val and
then you assign values using the equal
to symbol or the assignment operator
right and to this variable I want to
assign a string of text which is 5 is
different from 5 so this is the numeric
5 whereas this is the word 5 and if you
remember from the last tutorial there
are two ways in which you can create
string variables you can either create
using single quotes or double quotes and
if you create using double quotes you
can render your escape sequences whereas
if you create using single quotes then
the escape sequences don't work so over
here I have a challenge I want to have
double quotes around the word 5 and I
also want to render this escape sequence
so how do I do that because if I would
put a double quote here and a double
quote here then Paul would assume that
my string is going to end here and then
you know it's going to treat this part
as a string and then it's going to treat
this escape sequence is another string
and it won't know what these four or
five characters are doing between these
two strings so there has to be a way in
which I can make Perl know that this
double code is actually not the end of
the string that starts here and this
double code is also a part of the entire
and I do that by putting a slash before
my double quote so I would have to put a
slash here and a slash here and
everything would work just fine right on
line number four I am printing this
variable using the print statement so if
you've created a variable on one line
and you want to print it somewhere else
in your script you just have to use a
print statement give a space and put the
name of your variable of course you'll
have to terminate the statement using a
semicolon on line number six I have a
print statement which has two escape
sequences it has the slash a or the
alert bell escape sequence as well as
the slash in escape sequence I'm sure
you know what the /n sequence is used
for it's used to shift the cursor to a
newline the slash a escape sequence is
going to produce some sound on your
system whether you're using Mac Windows
or any operating system you would just
hear a beep or a tone or something on
line number eight we have the slash t
escape sequence this is known as the
horizontal tab and if I'm not wrong a
horizontal tab is equivalent to five
space characters so it would to a
horizontal tab escape sequences would
result into a horizontal gap of 10 space
characters and on line number 10 we have
the slash you escape sequence and you
know this is the slash small you escape
sequence so what this does is it changes
the case of the very next character to
uppercase if it's in lowercase and it
could be changed to uppercase if it's
already uppercase and it does nothing
and it changes the case of only one
character and not all following
characters for that we have the slash
upper us cave sequence which is on line
number 14 but before that on line number
12 we have the slash lower
l escaped sequence this one changes the
case of the character that follows
immediately to lowercase again if it's
already lowercase then it does nothing
and then on line number 16 we have the
slash capital L escape sequence which
changes the case of all following
characters to lowercase on
9:18 we have the slash capital u Q
escape sequence this one just puts a
slash before all non-alphanumeric or
all special characters basically if you
have special characters in your string
you're using the /q escape sequence then
you would have a slash before each and
every character right so I will run this
file and show you guys the output so you
will not be able to hear the beep
probably but you can see the formatting
effects that the escape sequences have
led to so you can see here that I have
double quotes around five and then you
know obviously the slash a escapes
escape sequence you'll be able to notice
the effect of that when you run the
script on your own system and then
between GA and P we have to slash the
escape sequences which have resulted
into the space and then the alphabet o
in one you can see that the case of this
particular character is uppercase
because we were using the slash you
escape sequence right here and then over
here we had the slash small L escape
sequence the world knew was all in
uppercase but because of this escape
sequence the alphabet n has been
displayed in lowercase and then this
entire statement if you can see online
but fourteen has been written in
lowercase
but because of this slash you escape
sequence the slash capital u escape
sequence before the word case the word
case is is displayed in uppercase and
then finally on line number 16 the slash
capital L escape sequence has resulted
into this word being displayed in small
case over here and the slash capital u Q
escape sequence has put a slash before
all special characters in this string so
that's it for this tutorial I am going
to see you in the next video in which we
continue our discussion on Perl concepts
I hope you guys had fun watching this
one and you
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