undefined valueのwarningsに疑問を感じったー
先日、コードの書き直しが必要になった際に文字列結合演算子を消し忘れ、
my $foo .= 'bar';
みたいなコードになっていたのですが、いつものwarningsが出ないので
いろいろと試してみましたよっと
#!/usr/bin/perl
use strict;
use warnings;
use lib q{.};
use Hoge;
print "Case:1$/";
my $foo;
$foo++;
print $/;
print "Case:2$/";
my $foo;
++$foo;
print $/;
print "Case:3$/";
my $foo .= 'bar';
print $/;
print "Case:4$/";
my $bar;
my $foo .= $bar;
print $/;
print "Case:5$/";
my $bar;
my $foo . $bar;
print $/;
print "Case:6$/";
my $foo .= Hoge->new();
print $/;
print "Case:7$/";
scalar(my $foo);
print $/;
print "Case:8$/";
length(my $foo);
print $/;
print "Case:9$/";
int(my $foo);
print $/;
print "Case:10$/";
ref(my $foo);
print $/;
print "Case:11$/";
lc(my $foo);
print $/;
print "Case:12$/";
uc(my $foo);
print $/;
print "Case:13$/";
select(my $foo);
select STDOUT;
print $/;
print "Case:14$/";
my $foo eq my $bar;
print $/;
print "Case:15$/";
my $foo == my $bar;
print $/;
print "Case:16$/";
my $foo ne my $bar;
print $/;
print "Case:17$/";
my $foo != my $bar;
print $/;
print "Case:18$/";
my $foo > 1;
print $/;
print "Case:19$/";
my $foo < 1;
print $/;
print "Case:20$/";
my $foo && my $bar;
print $/;
print "Case:21$/";
my $foo and 1;
print $/;
print "Case:20$/";
my $foo || my $bar;
print $/;
print "Case:21$/";
my $foo or 1;
print $/;
print "Case:22$/";
my $foo xor 1;
print $/;
print "Case:23$/";
my $foo >> 1;
print $/;
print "Case:24$/";
my $foo << 1;
print $/;
__END__これの出力結果が
Case:1 Case:2 Case:3 Case:4 Use of uninitialized value in concatenation (.) or string at test.pl line 28. Case:5 Use of uninitialized value in concatenation (.) or string at test.pl line 33. Use of uninitialized value in concatenation (.) or string at test.pl line 33. Case:6 Case:7 Case:8 Use of uninitialized value in length at test.pl line 45. Case:9 Use of uninitialized value in int at test.pl line 49. Case:10 Case:11 Case:12 Case:13 Case:14 Use of uninitialized value in string eq at test.pl line 70. Use of uninitialized value in string eq at test.pl line 70. Case:15 Use of uninitialized value in numeric eq (==) at test.pl line 74. Use of uninitialized value in numeric eq (==) at test.pl line 74. Case:16 Use of uninitialized value in string ne at test.pl line 78. Use of uninitialized value in string ne at test.pl line 78. Case:17 Use of uninitialized value in numeric ne (!=) at test.pl line 82. Use of uninitialized value in numeric ne (!=) at test.pl line 82. Case:18 Use of uninitialized value in numeric gt (>) at test.pl line 86. Case:19 Use of uninitialized value in numeric lt (<) at test.pl line 90. Case:20 Case:21 Case:20 Case:21 Case:22 Case:23 Use of uninitialized value in right bitshift (>>) at test.pl line 114. Case:24 Use of uninitialized value in left bitshift (<<) at test.pl line 118.
warningsプラグマ謎い。。。
