In this article, we delved into PERL's control structures and loops, covering essential topics for efficient programming. We began by exploring PERL operators as the foundation for control structures. Next, we examined If-Elsif-Else for decision-making, File Test Conditions for file handling, and the Unless structure as an alternative conditional approach, comparing it with If for clarity. Our loop exploration included the For Loop for range iteration, Foreach for arrays and lists, and While and Do-While Loops for condition-based execution. We also covered Until and Do-Until Loops for executing code until specific conditions are met and discussed Next and Last commands for precise loop control. By the end, readers gained a comprehensive understanding of PERL's control structures and loops, enabling them to write effective and streamlined code.
The For Loop in PERL :
- Initialization counter
- Condition checking counter
- Increment/decrement counter
The for loop has three counters (c-style) :
You can run it your end to see the output !
The ForEach Loop in PERL :
- Foreach operates on each element of an Array
- This array may come form Keys of a Hash/Associative-Array
- Some array operations(reverse/sort) are allowed in the foreach loop
- Default variable can take place if the element is not specified
- This array may be the default array of Arguments (@_)
It is very much self explanatory .
Here is an foreach code that you can run at your end :
This code iterates over the *.pl files in present directory. In VLSI Automation you may have to use such loops very frequently to iterate over files in a directory.
In the below example , we hand create a list and we iterate over it using the foreach loop :
This is a very common use of the foreach loop in PERL, however in most of the cases the list is not created by hand , instead it comes from some other part of the code as a output.
By Now you have noticed the difference of the for-loop and the foreach loop.
While and Do-While Loop in PERL :
You already know the while loop from c-language. Also you might be familiar with the do-while.
The functioning of the while loop is described in the below code snippet :
The code snippet is self explanatory as you read trough it.
The below code-snippet does your tour of the do-while loop functioning in PERL :
The meaning of the code snippet is self-explanatory.
Until and Do-until Loops in PERL :
The until loop continues executing as long as its test condition is false (i.e. until it becomes true).
The below code snippet explains the usage of the until and do-until loop :
The above code snippet is self-explanatory.
Loop Control : Next & Last
The Next and the Last serves the same purpose as continue and break keywords from c-language. Now it is new easier for you to understand the below points :
- The next and last operators allow you to modify the flow of your loop.
- It is not at all uncommon to have a special case; you may want to skip it, use next.
- Or a special case you want to quit when you encounter it, use last.
The code snippet mentioned above is self-explanatory.
The entire article is narrated in the video below :
Courtesy : Image by Jae Rue from Pixabay
