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perl concatenation assignment operator

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When interpolation is not the answer

X the repetition operator, ++ on a string.

Gabor Szabo

Published on 2014-05-01

Author: Gabor Szabo

perl concatenation assignment operator

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Perl | String Operators

Operators are the foundation of any programming language. Thus, the functionality of Perl programming language is incomplete without the use of operators. A user can define operators as symbols that help to perform specific mathematical and logical computations on operands. String are scalar variables and start with ($) sign in Perl. The String is defined by user within a single quote (‘) or double quote (“) . There are different types of string operators in Perl, as follows:  

  • Concatenation Operator (.)

Repetition Operator (x)

Auto-increment Operator (++)

Concatenation Operator(.)

Perl strings are concatenated with a Dot(.) symbol. The Dot(.) sign is used instead of (+) sign in Perl. This operator takes two scalars variables as operands and combines them in a single scalar variable. Both scalars i.e left and right will convert into a single string.  Example:  

Output:    

The x operator accepts a string on its left-hand side and a number on its right-hand side. It will return the string on the left-hand side repeated as many times as the value on the right-hand side. The repetition depends on the user’s input number. Syntax:  

Output:  

Note: Possible cases while using the Repetition Operator (x) in String as follows:   

  • $string xnumber : Gives Output
  • $string x number : Gives Output
  • $stringxnumber : Gives Error(where no space between string and x)
  • $stringx number : Gives Error(where no space between string and x)

Important Point to Remember: Both the Concatenation and Repetition operator can be used with assignment(=) operator as follows:  

  • Concatenation Assignment Operator (.=)
  • Repetition Assignment Operator (x=)

Example:  

   

This operator can also apply to strings. It is a unary operator thats why it will only take a single operand as string. The last character of the operand(i.e string) will increment by one using the ASCII values of characters. The important point to remember about ++ operator that if the string ends with ‘z or”Z’ then the result of ++ operator will be ‘a’ or ‘A’ respectively but the letter to the left of it will also increment by one as well. Example:    

   

What will happen if we pass an Alpha Numeric string with a number at last and try to increment it ? The number will be incremented by one just like it happened with the previous example –

Time Complexity – O(1)

Auxiliary Space – O(1)

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Perl string concatenation: How to concatenate strings with Perl

Perl string FAQ: How do I concatenate Perl strings?

When you work with Perl, you're often working with strings, and you’ll very often you need to concatenate strings. For instance, I recently had a need to create a temporary filename, and wanted to use the original filename as part of the temporary name.

I was going to get the first part of the filename (the filename prefix) by calling a function that generated temporary filenames. After getting the first part of the filename, I wanted to prepend the directory " /tmp/ " to the beginning of the name, and append the filename extension " .tmp " to the end of the name. Here's how I did it.

Perl string concatenation, Solution #1: Using ${name}

One of the best and simplest ways to concatenate Perl strings is with this syntax:

In this example, I have a Perl string variable named $name that contains the text " foo ", and I use this Perl syntax to embed the value of that variable in the string that I'm assigning to the new variable $filename . This example prepends the string ' /tmp/ ' to the variable $name, and appends the ' .tmp ' filename extension to $name .

These days I use this Perl string concatenation approach more than any other.

Perl string concatenation, Solution #2: Using Perl's dot operator

Another way to concatenate Perl strings is to use the "dot" operator (i.e., the decimal character). In some circumstances it can make your Perl script easier to read than the syntax shown above.

To concatenate Perl strings this way, just place the dot operator in between the strings you want to merge on the right side of the '=' symbol in your statement, as shown here:

Again, this example creates a Perl variable named $filename that contains the concatenated string contents shown on the right side of that statement.

Perl string concatenation, Solution #3: Using Perl's join function

Another way to create the desired variable $filename is to use the Perl join function. With the join function you can merge as many Perl strings together as you like, and you can specify what token you want to use to separate each string.

The code shown in Listing 2 below uses the Perl join function to achieve the same result as the code shown in Listing 1:

I rarely use the Perl join function to merge simple strings like this, but I thought I'd show this as another possible way to concatenate Perl strings.

Perl string concatenation: Summary

I hope these Perl string concatenation examples have been helpful. I just updated this article in 2011 to update it to the current Perl "best practices".

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