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Perl nested Loop
A loop can be nested inside of another loop. Perl allows to nest all type of loops to be nested.
Syntax
The syntax for a nested for loop statement in Perl is as follows −
for ( init; condition; increment ) { for ( init; condition; increment ) { statement(s); } statement(s); } The syntax for a nested while loop statement in Perl is as follows −
while(condition) { while(condition) { statement(s); } statement(s); } The syntax for a nested do...while loop statement in Perl is as follows −
do{ statement(s); do{ statement(s); }while( condition ); }while( condition ); The syntax for a nested until loop statement in Perl is as follows −
until(condition) { until(condition) { statement(s); } statement(s); } The syntax for a nested foreach loop statement in Perl is as follows −
foreach $a (@listA) { foreach $b (@listB) { statement(s); } statement(s); } Example
The following program uses a nested while loop to show the usage −
#/usr/local/bin/perl $a = 0; $b = 0; # outer while loop while($a < 3) { $b = 0; # inner while loop while( $b < 3 ) { print "value of a = $a, b = $b\n"; $b = $b + 1; } $a = $a + 1; print "Value of a = $a\n\n"; } This would produce the following result −
value of a = 0, b = 0 value of a = 0, b = 1 value of a = 0, b = 2 Value of a = 1 value of a = 1, b = 0 value of a = 1, b = 1 value of a = 1, b = 2 Value of a = 2 value of a = 2, b = 0 value of a = 2, b = 1 value of a = 2, b = 2 Value of a = 3
perl_loops.htm
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