How do you print "undef" for array elements that are undefined?
#! /usr/bin/env perl
use warnings;
use strict;
use utf8;
use feature qw<say>;
my @a1 = 1..8;
my @a2 = (4143, undef, 8888);
my @a3 = qw<a b c>;
say "@a1 and @a2 and @a3";
exit(0);
This outputs:
Use of uninitialized value $a2[1] in join or string at ./my.pl line 12.
1 2 3 4 5 6 7 8 and 4143 8888 and a b c
But I'd like it to output (without warnings)
1 2 3 4 5 6 7 8 and 4143 undef 8888 and a b c
Answer
One way to print the string "undef" in place of an undefined array item is to check if the item is defined:
use warnings;
use strict;
use utf8;
use feature qw<say>;
my @a1 = 1..8;
my @a2 = (4143, undef, 8888);
my @a3 = qw<a b c>;
for (@a1, @a2, @a3) {
$_ = 'undef' unless defined $_;
print "$_ ";
}
print "\n";