Perl Tutorial - 29: Do While Loop Video Lecture | Perl Building Blocks: An Introduction to Perl - Back-End Programming

hello guys welcome to my channel this is
the 29th route all in this course and in
this tutorial we'll be talking about the
do-while loop in Perl
so the do-while loop is an exit control
loop and it is different from the while
or for loop in the sense that in while
loop we evaluate the test condition to
decide whether we want to execute the
code that's in the body of the loop or
not in do-while loop we execute the code
in the body at least once before
checking for the test condition you know
so even if the condition is false at the
beginning we are going to have at least
one eye tration of the loop so to
demonstrate the syntax I have a file
here that's called do-while and in this
file on line number 3 I have created
scalar variable that's called X and it
has the value 10 and on nine number five
I have a keyword do and on line number
six I have an opening curly brace to
mark the beginning of the the body of
the loop on line number nine I have the
corresponding closing curly brace and I
also have the keyword while immediately
after the brace right and this is where
you put the while keyword along with the
test condition so my condition is X is
less than equal to 20 and it should work
the same way as the while loop you know
this is familiar code we've seen it in
the past inside the body of the loop I'm
not doing anything fancy I'm just
printing the value of X and I'm also
updating X so that you know this
condition eventually becomes false so
let me run this script to show you the
output you know there we go we see
numbers from 10 to 19 and this is the
exact output that we got with the the
while loop you know when we had similar
code inside the body of the loop but
things become interesting when I give X
initial value of hundreds so we know
that hundred is not less than 20 so this
condition is false at the offset if we
were using while loop then you
we wouldn't have gotten any output for
this script but since we are using
do-while loop and as I mentioned that
even if the test condition is false we
will have at least one eye tration when
we run the code we see 100 on screen and
that's because we got to this point and
immediately we went inside the body of
the loop we printed the current value of
x which is 100 we updated X so X became
101 and then we got to the wild part
where the condition was checked X wasn't
found to be less than 20 and you know we
didn't have any more iterations but you
know since this is due while we at least
printed the value of X once so the you
why is this useful it's useful because
there could be situations in which you
want to do something at least once like
you know if you are building a program
that displays menu to users on screen
with an option to exit then you would
want the user to at least see the menu
before deciding to you know do something
with your program interact with it or
you know simply press whatever key or
you know provide input to exit and you
know it's it's a pro it's a programming
concept that is not present just in Perl
but in almost all programming languages
it's it's it's a very useful thing and
this is how you use it in Perl so that's
it for this tutorial I hope you guys had
fun watching this one 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