Using postfix conditionals and loops in perl

Conditional & loop statements are a standard & integral part of any programming language. These type of statements follow a somewhat standard syntax. In case of a conditional statement we write a statement to have the condition checked & another statement performing an action based on the result of the condition. In case of a loop statement we first write a statement for defining the loop i.e. the conditions under which the loop will continue to iterate followed by the action performed as a result of the loop execution.

Perl offers a non-standard unique feature of defining the action to performed before mentioning the condition/loop statement. Although this is valid only when the conditional/loop block does not span more than a single statement i.e. we are performing a single action like printing the contents on an array via a foreach loop.

Here is a sample code demonstrating various usage examples for postfix conditional & loop statements along with an example for last & next statement as well.

The next statement is used to skip a match within the loop & the last statement terminates the loop when the match if found.

[root@cent6 ~]# cat post.pl
#!/usr/bin/perl -w
#
my @art = ("one", "two", "three", "four", "five") ;

print "postfix foreach example \n";
print "$_ \n" foreach (@art) ;

print "postfix if example \n";

my $a = 10;
my $b = 20;

print "true \n" if ($a < $b) ;

print "postfilx while example \n" ;

my @art2 = qw (unix linux debian) ;

print shift @art2, "\n"  while (@art2) ;

print "postfix next & last example \n" ;

my @art3 = qw (1 2 3 4 5 6 7 8) ;

print "next statement example \n" ;

foreach (@art3) {
        next if ($_ == 2) ;
        print "$_ \n" ;
        }

print "last statement example \n" ;

foreach (@art3) {
        last if ($_ == 4) ;
        print $_, "\n" ;
        }

The above script shows the following output when executed:

[root@cent6 ~]# ./post.pl

postfix foreach example

one

two

three

four

five

postfix if example

true

postfilx while example

unix

linux

debian

postfix next & last example

next statement example

1

3

4

5

6

7

8

last statement example

1

2

3

[root@cent6 ~]#

This may not sound very useful at first but it can help make your perl scripts significantly shorter when used appropriately.