Perl 初始化值 : "" vs q{} and 0 vs (1==2)

Question

my $EMPTY = q{};
use constant TRUE  => ( 1==1 );
use constant FALSE => ( 1==2 );


my $a = "";   vs my $a = $EMPTY;             
my $b = 0;    vs my $b = FALSE

应该使用哪个而不是什么有什么区别吗？
它取决于某些情况吗？
如果是这样，关于您何时希望使用 my $b = 0; 的情况是什么？在 my $b = FALSE反之亦然？

Answer 1

""和 q{}两者都产生一个零长度的字符串。

>perl -MDevel::Peek -e"$_ = q{}; Dump($_);"
SV = PV(0x306748) at 0x4c9058
  REFCNT = 1
  FLAGS = (POK,pPOK)            <--- Contains a string.
  PV = 0x4ac9e8 ""\0
  CUR = 0                       <--- Length of the string is zero.
  LEN = 16

0产生数字零。

>perl -MDevel::Peek -e"$_ = 0; Dump($_)"
SV = IV(0x229088) at 0x229098
  REFCNT = 1
  FLAGS = (IOK,pIOK)            <--- Contains a signed integer.
  IV = 0                        <--- Contained integer is zero.

(1==2)产生一个包含空字符串和数值零的标量。

>perl -MDevel::Peek -e"$_ = 1==2; Dump($_);"
SV = PVNV(0x1fc598) at 0x259038
  REFCNT = 1
  FLAGS = (IOK,NOK,POK,pIOK,pNOK,pPOK)   <--- A signed int, a float and a str.
  IV = 0                        <--- Contained integer is zero.
  NV = 0                        <--- Contained floating point number is zero.
  PV = 0x23ca18 ""\0
  CUR = 0                       <--- Length of the string is zero.
  LEN = 16