Inside CGI.pm,how does thingies like END_OF_FUNC work?

3643 '_compile_al开发者_JS百科l' => <<'END_OF_FUNC',
3644 sub _compile_all {
3645     foreach (@_) {
3646         next if defined(&$_);
3647         $AUTOLOAD = "CGI::$_";
3648         _compile();
3649     }
3650 }
3651 END_OF_FUNC
3652
3653 );
3654 END_OF_AUTOLOAD
3655 ;

How does END_OF_FUNC and END_OF_AUTOLOAD work here?

That is here-doc syntax, it is just a way of writing strings.

It's part of the nearly-obsolete AutoLoader mechanism, which tries to save a tiny amount of time by only defining functions when they're first referenced. It's preserved in CGI primarily for compatibility reasons; there's no good reason to write any new code this way.