Perl UNLESS...ELSE Statement
Perl Conditional StatementsAn unless statement can be followed by an optional else statement, which executes when the boolean expression is true.
Syntax
The syntax format is as follows:
unless(boolean_expression){
# 在布尔表达式 boolean_expression 为 false 执行
}else{
# 在布尔表达式 boolean_expression 为 true 执行
}
If the boolean expression boolean_expression is false, the code inside the unless block is executed. If the boolean expression is true, the code inside the else block is executed.
Flowchart
Example
Example
#!/usr/bin/perl
$a = 100;
# Use the unless statement to test the boolean expression
unless( $a == 20 ){
# Executes when the boolean expression is false
printf "The given condition is false\n";
}else{
# Executes when the boolean expression is true
printf "The given condition is true\n";
}
print "The value of a is :$a\n";
$a = "";
# Use the unless statement to test the boolean expression
unless( $a ){
# Executes when the boolean expression is false
printf "The given condition for a is false\n";
}else{
# Executes when the boolean expression is true
printf "The given condition for a is true\n";
}
print "The value of a is :$a\n";
Executing the above program produces the following output:
给定的条件为 false a 的值为 : 100 a 给定的条件为 false a 的值为 :Other Extensions