Perl loop nesting

Author：Eve Cole Update Time：2025-01-03 13:24:01

The Perl language allows the use of a loop within another loop. Here are a few examples to illustrate this concept.

grammar

Syntax for nested for loop statements:

for ( init ; condition ; increment ) { for ( init ; condition ; increment ) { statement ( s ) ; } statement ( s ) ; }

Syntax of nested while loop statement:

while ( condition ) { while ( condition ) { statement ( s ) ; } statement ( s ) ; }

Syntax of nested do...while loop statements:

do { statement ( s ) ; do { statement ( s ) ; } while ( condition ) ; } while ( condition ) ;

Syntax for nested until loop statements:

until ( condition ) { until ( condition ) { statement ( s ) ; } statement ( s ) ; }

Syntax of nested foreach loop statement:

foreach $a ( @listA ) { foreach $b ( @listB ) { statement ( s ) ; } statement ( s ) ; }

Example

#!/usr/bin/perl $a = 0 ; $b = 0 ; # Outer loop while ( $a < 3 ) { $b = 0 ; # inner loop while ( $b < 3 ) { print " a = $a , b = $b n " ; $b = $b + 1 ; } $a = $a + 1 ; print " a = $a n n " ; }

Executing the above program, the output result is:

 a = 0, b = 0a = 0, b = 1a = 0, b = 2a = 1a = 1, b = 0a = 1, b = 1a = 1, b = 2a = 2a = 2, b = 0a = 2, b = 1a = 2, b = 2a = 3