Back-End Programming Exam > Back-End Programming Videos > Perl Building Blocks: An Introduction to Perl > Perl Tutorial - 50: Private Variables
Perl Tutorial - 50: Private Variables Video Lecture | Perl Building Blocks: An Introduction to Perl - Back-End Programming
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FAQs on Perl Tutorial - 50: Private Variables Video Lecture - Perl Building Blocks: An Introduction to Perl - Back-End Programming
| 1. What are private variables in Perl? |  |
| 2. How are private variables different from global variables in Perl? | |
Ans. Private variables are only accessible within a specific scope, such as a block or subroutine, while global variables can be accessed from anywhere in the program. Private variables are declared using the "my" keyword, whereas global variables are declared using "our" or are not declared at all.
| 3. How can I declare and use private variables in Perl? | |
Ans. To declare a private variable in Perl, use the "my" keyword followed by the variable name. For example, "my $privateVariable = 10;". To use the private variable within the same scope, simply refer to it by its name. It is not accessible outside the defined scope.
| 4. Can I access private variables from another package or module in Perl? | |
Ans. No, private variables are not accessible from another package or module in Perl. They are limited to the scope in which they are defined. If you need to access the value of a private variable in another package or module, you can create accessor methods or use other mechanisms like passing the variable as a parameter.
| 5. Are private variables necessary in Perl? | |
Ans. Private variables provide encapsulation and data hiding, which can be beneficial in maintaining code integrity and preventing unintended modifications. While not strictly necessary, using private variables can help organize and protect your code by limiting the scope of variables to where they are needed.
Text Transcript from Video
hello guys welcome to my channel this is
the 50th 50 total in this course and in
this little we're going to talk about
private variables in Perl so I have a
script here that's called my underscore
Val and in this script on line number 3
I have created a variable a scalar
variable called vert and I have assigned
to it the value 500 and then on line
number 5 I have created a subroutine
called Tech's sorry tests and then in
sight
the definition for this subroutine I
have created another instance of the
variable Val it's just at this time I
have done it using the keyword my and
you know I have also assigned a
different value to the variable this
time I have assigned 50 to it and then
on line number 8 I have a print
statement that's first going to display
the text value of variable inside the
subroutine and then I have printed the
contents of door over there and then
outside the subroutine on line number 10
I have made a call to the subroutine and
it does not accept any argument so you
know I haven't passed anything within
the parentheses just the name of the
subroutine with a set of empty
parentheses and the semicolon is going
to make a call and then on line number
11 I have another print statement that's
going to first display the text value of
variable outside the subroutine and then
it's going to push out the contents of
the variable bad so what do you think is
going to happen the first instance of
this variable is on line number 3 where
we've assigned to it the value 500 and
then inside the subroutine again on line
number 7 we are trying to change the
value to 50 but is this change going to
apply or not remains to be seen
so before we talk about what the my
keyword is for let me show you the
output of the script so we see that the
value of variable inside the subroutine
is 50 and the value of variable outside
the subroutine is 500 so you know that
is what the my keyword does it makes the
variable private to the subroutine so
when you make a call to the subroutine
on line number 10 it's going to
you know treat this variable VAD as a
local variable to this subroutine
because we are using the keyword my hair
and it's going to change the value to 50
there is no problem with this and of
course when you try to print the value
from within the subroutine it's going to
display the value that is known to the
subroutine and that is 50
the thing is when this value is changed
you also have a print statement on line
number 11 so you know the value for val
is changed to 50 and that's the value
that we should see here as well but here
we see 500 and the reason for that is
that this change you know the change
from 500 to 50 is only valid within the
subroutine because of the keyword my and
you know as I said this variable becomes
private to the subroutine as a result of
which whatever value you pass to it here
is only going to be known till the time
this subroutine is being executed as
soon as you move out of the subroutine
and you get to the print statement on
line number 11 it's going to forget this
value 50 because we are no longer within
tests private space and we're gonna
fetch the global value 500 which we have
assigned on line number 3 and that
explains the output so the value of
variable inside the subroutine is 500
and the value of Abell outside the
subroutine sorry inside it's 50 and
outside is 500 I hope you guys had fun
watching this tutorial you may subscribe
to my channel if you haven't already I'm
gonna see you in the next video till
then take care
the 50th 50 total in this course and in
this little we're going to talk about
private variables in Perl so I have a
script here that's called my underscore
Val and in this script on line number 3
I have created a variable a scalar
variable called vert and I have assigned
to it the value 500 and then on line
number 5 I have created a subroutine
called Tech's sorry tests and then in
sight
the definition for this subroutine I
have created another instance of the
variable Val it's just at this time I
have done it using the keyword my and
you know I have also assigned a
different value to the variable this
time I have assigned 50 to it and then
on line number 8 I have a print
statement that's first going to display
the text value of variable inside the
subroutine and then I have printed the
contents of door over there and then
outside the subroutine on line number 10
I have made a call to the subroutine and
it does not accept any argument so you
know I haven't passed anything within
the parentheses just the name of the
subroutine with a set of empty
parentheses and the semicolon is going
to make a call and then on line number
11 I have another print statement that's
going to first display the text value of
variable outside the subroutine and then
it's going to push out the contents of
the variable bad so what do you think is
going to happen the first instance of
this variable is on line number 3 where
we've assigned to it the value 500 and
then inside the subroutine again on line
number 7 we are trying to change the
value to 50 but is this change going to
apply or not remains to be seen
so before we talk about what the my
keyword is for let me show you the
output of the script so we see that the
value of variable inside the subroutine
is 50 and the value of variable outside
the subroutine is 500 so you know that
is what the my keyword does it makes the
variable private to the subroutine so
when you make a call to the subroutine
on line number 10 it's going to
you know treat this variable VAD as a
local variable to this subroutine
because we are using the keyword my hair
and it's going to change the value to 50
there is no problem with this and of
course when you try to print the value
from within the subroutine it's going to
display the value that is known to the
subroutine and that is 50
the thing is when this value is changed
you also have a print statement on line
number 11 so you know the value for val
is changed to 50 and that's the value
that we should see here as well but here
we see 500 and the reason for that is
that this change you know the change
from 500 to 50 is only valid within the
subroutine because of the keyword my and
you know as I said this variable becomes
private to the subroutine as a result of
which whatever value you pass to it here
is only going to be known till the time
this subroutine is being executed as
soon as you move out of the subroutine
and you get to the print statement on
line number 11 it's going to forget this
value 50 because we are no longer within
tests private space and we're gonna
fetch the global value 500 which we have
assigned on line number 3 and that
explains the output so the value of
variable inside the subroutine is 500
and the value of Abell outside the
subroutine sorry inside it's 50 and
outside is 500 I hope you guys had fun
watching this tutorial you may subscribe
to my channel if you haven't already I'm
gonna see you in the next video till
then take care
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Apr 18, 2025
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