Issue #8110 has been updated by sam.saffron (Sam Saffron).


A slight concern here is naming, since: 

  rb_define_virtual_variable("$~", match_getter, match_setter);
    rb_define_virtual_variable("$&", last_match_getter, 0);
    rb_define_virtual_variable("$`", prematch_getter, 0);
    rb_define_virtual_variable("$'", postmatch_getter, 0);
    rb_define_virtual_variable("$+", last_paren_match_getter, 0);

    rb_define_virtual_variable("$=", ignorecase_getter, ignorecase_setter);
    rb_define_virtual_variable("$KCODE", kcode_getter, kcode_setter);
    rb_define_virtual_variable("$-K", kcode_getter, kcode_setter);

even though core uses the term backref quite extensively, often people can confuse it with:

"round brackets also create a "backreference". A backreference stores the part of the string matched by the part of the regular expression inside the parentheses." 

see: http://www.regular-expressions.info/brackets.html 

I wonder if a different term all together should leak out Regexp::SKIP_GLOBALS and /foo/S , this is far more explicit and clear to explain. 


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Feature #8110: Regex methods not changing global variables
https://bugs.ruby-lang.org/issues/8110#change-38129

Author: prijutme4ty (Ilya Vorontsov)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: next minor


It is useful to have methods allowing pattern matching without setting global variables. It can be very hard to understand where the problem is when you for example insert a string like `puts pat === my_str` and your program fails in a place which is far-far away from inserted place. This can happen due to replacing global variables of previous pattern match. I caught to this when placed pattern-match inside case-statement and shadowed global vars which were initially filled by match in when-statement.
For now one can extract pattern matching into another method thus defining method-scope for that variables. But sometimes it looks like an overkill. May be simple method like #match_globalsafe can prevent that kind of errors. At least when a programmer see such a method in a list of methods, he's warned that usual match can cause such problems.


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