Perl String

Summary: in this tutorial, you’ll learn about the Perl strings and how to manipulate strings using built-in string functions.

Perl StringIntroduction to Perl strings

In Perl, a string is a sequence of characters surrounded by some kinds of quotation marks. A string can contain ASCII, UNICODE and escape sequences characters such as \n.

A Perl string has the length that depends on the amount of memory in your system, which is theoretically unlimited.

The following example demonstrates single and double-quoted strings.

my $s1 = "string with doubled-quotes"; my $s2 = 'string with single quote';
Code language: Perl (perl)

It is important to remember that the double-quoted string replaces variables inside it by their values, while the single-quoted string treats them as text. This is known as the variable interpolation in Perl.

Perl string alternative delimiters

Besides the single and double-quotes, Perl also allows you to use quote-like operators such as:

  • The  q// acts like single-quoted string.
  • The  qq// acts like double-quoted string.

You can choose any non-alphabetic and non-numeric characters as the delimiters, not only just characters //.

See the following example:

#!/usr/bin/perl use warnings; use strict; my $s= q/"Are you learning Perl String today?" We asked./; print($s ,"\n"); my $name = 'Jack'; my $s2 = qq/"Are you learning Perl String today?"$name asked./; print($s2 ,"\n");
Code language: Perl (perl)

How it works.

  • First, defined a single-quoted string variable with the quote-like operator q/. The string  $s ends with /.
  • Second, defined a double-quoted string with the quote-like operator qq/. In this case, we used the  $name variable inside a string and it is replaced by its value, Jack.

The following example demonstrates string with the  ^ delimiter.

#!/usr/bin/perl use warnings; use strict; my $s = q^A string with different delimiter ^; print($s,"\n");
Code language: Perl (perl)

Perl string functions

Perl provides a set of functions that allow you to manipulate strings effectively. We cover the most commonly used string functions in the following section for your reference.

Perl string length

To find the number of characters in a string, you use the length() function. See the following example:

my $s = "This is a string\n"; print(length($s),"\n"); #17
Code language: Perl (perl)

Changing cases of string

To change the cases of a string you use a pair of functions  lc() and  uc() that returns the lower case and upper case versions of a string.

my $s = "Change cases of a string\n"; print("To upper case:\n"); print(uc($s),"\n"); print("To lower case:\n"); print(lc($s),"\n");
Code language: Perl (perl)

Search for a substring inside a string

To search for a substring inside a string, you use  index() and  rindex() functions.

  • The  index() function searches for a substring inside a string from a specified position and returns the position of the first occurrence of the substring in the searched string. If the position is omitted, it searches from the beginning of the string.
  • The  rindex() function works like the  index() function except it searches from the end of the string instead of from the beginning.

The following example demonstrates how to use the  index() and rindex() functions:

#!/usr/bin/perl use warnings; use strict; my $s = "Learning Perl is easy\n"; my $sub = "Perl"; my $p = index($s,$sub); # rindex($s,$sub); print(qq\The substring "$sub" found at position "$p" in string "$s"\,"\n");
Code language: Perl (perl)

Get or modify substring inside a string

To extract a substring out of a string, you use the  substr() function.

#!/usr/bin/perl use warnings; use strict; # extract substring my $s = "Green is my favorite color"; my $color  = substr($s, 0, 5);      # Green my $end    = substr($s, -5);        # color print($end,":",$color,"\n"); # replace substring substr($s, 0, 5, "Red"); #Red is my favorite color print($s,"\n");
Code language: Perl (perl)

Other useful Perl string functions

The following table illustrates other useful Perl string functions with their descriptions:

chrReturn ASCII or UNICODE character of a number
cryptEncrypts password in one way fashion
hexConverts a hexadecimal string to the corresponding value
indexSearches for a substring inside a string returns position where the first occurrence of the substring found
lcReturns a lowercase version of string
lengthReturns the number of characters of a string
octConverts a string to an octal number
ordReturns the numeric value of the first character of a string
q/string/Creates single-quoted strings
qq/string/Creates double-quoted strings
reverseReverses a string
rindexSearches for a substring from right to left
sprintfFormats string to be used with print()
substrGets or modifies a substring in a string
ucReturns the uppercase version of the string

In this tutorial, you’ve learned about Perl string and used string functions to manipulate strings effectively.

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