Perl Tutorial - 2: Comments & Quotes Video Lecture | Perl Building Blocks: An Introduction to Perl - Back-End Programming

hello guys welcome to my channel this is
the second tutorial in the series of
your dolls on purl and in this tutorial
we'll be talking about comments as well
as the difference between single and
double quotes in purl so to get started
I have a script opened up in my IDE here
it's called quotes and it has the
extension dot PL and in this file
I have several print statements and
along with the print statements I have
some other statements like I've got two
comments here and then I've got the
shebang line on line number one and then
I've also got a variable declaration and
assignment on line number nine
so I've got lot of fancy stuff and we're
going to talk about some or maybe all of
whatever I have in the script in greater
detail in the future tutorials but for
the time being I just want to highlight
a couple of things so you know let's
just get going so to create a comment in
Perl you use the hash symbol or the
pound symbol and I want you to take note
of the text I have on line number three
a comment is a string of text that you
include in your program to just make it
more comprehensible so that if you are
looking at your code six months later
you know what's going on in your program
or if someone else is looking at your
code then the person can maybe better
understand whatever you've written and I
have a comment that spreads over two
lines so in some programming languages
like C++ you know you have a way of
making a comment multi-line in Perl we
do things really simple by putting a
hash at the beginning of any line which
is a comment right so this line is
supposed to be a comment that's why I've
got a pound symbol here and this one's
supposed to be a comment as well so this
is a comment and it will just be ignored
by Perl and on line number six I've got
a print statement this is very similar
to the print statement that I had in the
previous script the one that we checked
out in the last tutorial so this is
going to display the text hello world
and this thing this combination of
characters the slash and the alphabet n
is actually a newline escape sequence
and what this does is after printing the
text hello world it shifts the cursor to
the next line right that's what this
does if suppose you would put this at
the beginning of hello world then even
before the text hello world is printed
the cursor would automatically move to
the next line and the escape sequence /n
or for that matter any escape sequence
would work only if you enclose the
escape sequence within double quotes so
if you are printing using the print
statement you have to ensure that your
your text that has the escape sequences
enclosed within double quotes only then
will it be interpreted otherwise it
would just be displayed so to highlight
that difference on line number seven I
have a similar print statement but this
one has a text enclosed within single
quotes and not in double quotes so
slashing is going to be displayed and
the cursor will actually not be shifted
to the newline as a result of this then
on line number nine I have created a
variable called my underscore very and
we are going to talk about variables in
more detail later on
but in Perl we create variables by using
the dollar symbol so you put the dollar
symbol and then give a name for your
variable I have called it my underscore
Val and then if you want to give it a
numeric value you just put the equal to
sign put the value that you want to give
to it and then just terminate the
statement with a semicolon right on line
number 11 I am going to try to print the
value of this variable using the print
statement so for that I am first going
to display some text right and since
this is not going to result into the
cursor moving to the next line I have a
slash in escape sequence at the
beginning of the text in this print
statement so we are going to print value
of my variable a colon and then I am
just going to type the dollar symbol and
the name of my variable to get the value
right so you don't have to put a dot
here concatenation or whatever nothing
is required you just put a dollar symbol
and the name of your variable and then
after that if you want to print more
strings then you know just simply type
type the text on line number 12 I have
another print statement this one has
is a the same thing going on it's just
that instead of double quotes I have
single quotes and like escape sequences
if you're using single quotes with the
print statement the values of variables
are not displayed so instead of seeing
the value that's stored in my value are
actually just going to see the text
dollar my underscore var so any way I
can show you the output of this script
so this is how it is line number six
results into hello world and then as a
result of this escape sequence we've got
the cursor on the next line and then on
line number seven I have a print
statement which is in single quotes the
text hello world with the escape
sequences and single quotes so we see
the text but the escape sequence has not
been rendered so we see slash n instead
of the cursor moving on to the next
position and this not appearing here we
see this and then since we are not
printing this on line number nine just
the variable has been created and then
on line number eleven I have a print
statement to see the text value of my
variable and then we are seeing the
value 20 whereas the print statement
that I have on line number 12 is showing
me the text value of my variable but
instead of showing me the value it's
just displaying the name of the variable
right so I hope we have managed to
understand the difference between single
and double quotes in Perl and we're
going to talk about some of these
concepts later on as well hope you had
fun watching this tutorial you may
subscribe to my channel if you haven't
already I'm going to see you in the next
video till then take care