Hi friends! In our last blog learning session, we grabbed
some knowledge about the flow of control in PERL programming by using ‘if-else’
statements. Let us understand today these ‘if-else’ statements by means of some
examples.
Consider you are asked to build a program which can classify
the customers in a bank as premium, important and regular customer on the basis
of the balance they have in their bank accounts. Classification is to be made
like this:
This problem can be converted into a PERL program which
can be used to distinguish the various classes of customers. Let us see how it
is done:
if ($balance > 1000000)
{
print “\nPremium Customer.”;
}
elsif ($balance > 500000)
{
print “\nImportant Customer.”;
}
else
{
Print “\nRegular Customer.”;
}
In the program illustrated above, the flow is designed in
such a way that there is the need of only one condition to be specified in the
body of execution. ‘Body of Execution’ is the block below each condition, it is
included in the curly-brackets ( { <body> } ).
One more thing to notice here is that we do not put
terminator (;) after the if or elsif or else statement. It is because the
statement as a whole does not terminates at the same line, if found correct, it’s
body will be executed, which is in the next line starting with ‘{‘ and ending
with ‘}’. It is a common mistake to put terminator after the flow statement.
One more that I want to discuss today is the use of
comments in our programs. Suppose you are working on a big-big and complex
program which uses various formulae and statements. It is a usual thing that
you may not be able to grasp your own coding if viewed later. So, to keep our
program meaningful to us and to other programmers, we use some statements which
help us in grabbing the idea about our program. These statements are completely
ignored by the PERL interpreter.
In PERL, comments begin with ‘#’ symbol. In other words,
if you put ‘#’ in a line, all the characters after become invisible to
interpreter. Let us re-write the above program using comments to make it more
illustrative.
if ($balance > 1000000)
# first condition
{
print “\nPremium Customer.”; #
Body of first condition
}
elsif ($balance > 500000)
# second condition
{
print “\nImportant Customer.”;
# Body of second condition
}
Else # Final condition
{
Print “\nRegular Customer.”; # Body
of final condition
}
This concludes today’s learning session on PERL learning
blog. Hope you are finding these learning sessions interesting and easy to
understand.
With Warm Regards,
Yajur Kumar
(PERL Programming Expert)
Yajur Kumar
(PERL Programming Expert)
