gsub

/*
 *  call-seq:
 *     gsub(pattern, replacement)    => string
 *     gsub(pattern) {|...| block }  => string
 *  
 *  Equivalent to <code>$_.gsub...</code>, except that <code>$_</code>
 *  receives the modified result.
 *     
 *     $_ = "quick brown fox"
 *     gsub /[aeiou]/, '*'   #=> "q**ck br*wn f*x"
 *     $_                    #=> "q**ck br*wn f*x"
 */

static VALUE
rb_f_gsub(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE str = rb_str_dup(uscore_get());

    if (NIL_P(rb_str_gsub_bang(argc, argv, str)))
        return str;
    rb_lastline_set(str);
    return str;
}