perl - 为什么 Perl CGI 模块使用连字符开始命名参数？

Question

我是新手。我的问题是键(类型、过期名称等)前的“-”代表什么？为什么不直接使用简单的哈希表方式并丢弃连字符？

# #!/usr/local/bin/perl -w
use CGI; 
$q = CGI->new; 
print $q->header(-type=>'image/gif',-expires=>'+3d');
$q->param(-name=>'veggie',-value=>'tomato');

Answer 1

作者已经解释了in the documentation .

Most CGI.pm routines accept several arguments, sometimes as many as 20 optional ones! To simplify this interface, all routines use a named argument calling style that looks like this:

print $q->header(-type=>'image/gif',-expires=>'+3d');

Each argument name is preceded by a dash. Neither case nor order matters in the argument list. -type, -Type, and -TYPE are all acceptable. In fact, only the first argument needs to begin with a dash. If a dash is present in the first argument, CGI.pm assumes dashes for the subsequent ones.

Several routines are commonly called with just one argument. In the case of these routines you can provide the single argument without an argument name. header() happens to be one of these routines. In this case, the single argument is the document type.

print $q->header('text/html');