+/(.)/; # untaint $&, $`, $', $+, $1.
+check_taint_not $&, "\$& from /(.)/";
+
+"0" =~ /(\d)/; # taint $&, $`, $', $+, $1.
+check_taint $&, "\$& from /(\\d)/";
+check_taint $`, "\t\$`";
+check_taint $', "\t\$'";
+check_taint $+, "\t\$+";
+check_taint $1, "\t\$1";
+check_taint_not $2, "\t\$2";
+
+/(.)/; # untaint $&, $`, $', $+, $1.
+check_taint_not $&, "\$& from /(.)/";
+
+/(\D)/; # taint $&, $`, $', $+, $1.
+check_taint $&, "\$& from /(\\D)/";
+check_taint $`, "\t\$`";
+check_taint $', "\t\$'";
+check_taint $+, "\t\$+";
+check_taint $1, "\t\$1";
+check_taint_not $2, "\t\$2";
+
+/(.)/; # untaint $&, $`, $', $+, $1.
+check_taint_not $&, "\$& from /(.)/";
+
+/([[:alnum:]])/; # taint $&, $`, $', $+, $1.
+check_taint $&, "\$& from /([[:alnum:]])/";
+check_taint $`, "\t\$`";
+check_taint $', "\t\$'";
+check_taint $+, "\t\$+";
+check_taint $1, "\t\$1";
+check_taint_not $2, "\t\$2";
+
+/(.)/; # untaint $&, $`, $', $+, $1.
+check_taint_not $&, "\$& from /(.)/";
+
+/([[:^alnum:]])/; # taint $&, $`, $', $+, $1.
+check_taint $&, "\$& from /([[:^alnum:]])/";
+check_taint $`, "\t\$`";
+check_taint $', "\t\$'";
+check_taint $+, "\t\$+";
+check_taint $1, "\t\$1";
+check_taint_not $2, "\t\$2";
+
+"a" =~ /(a)|(\w)/; # taint $&, $`, $', $+, $1.
+check_taint $&, "\$& from /(a)|(\\w)/";
+check_taint $`, "\t\$`";
+check_taint $', "\t\$'";
+check_taint $+, "\t\$+";
+check_taint $1, "\t\$1";
+ok($1 eq 'a', ("\t" x 5) . "\$1 is 'a'");
+ok(! defined $2, ("\t" x 5) . "\$2 is undefined");
+check_taint_not $2, "\t\$2";
+check_taint_not $3, "\t\$3";
+
+/(.)/; # untaint $&, $`, $', $+, $1.
+check_taint_not $&, "\$& from /(.)/";
+
+"\N{CYRILLIC SMALL LETTER A}" =~ /(\N{CYRILLIC CAPITAL LETTER A})/i; # no tainting because no locale dependence
+check_taint_not $&, "\$& from /(\\N{CYRILLIC CAPITAL LETTER A})/i";
+check_taint_not $`, "\t\$`";
+check_taint_not $', "\t\$'";
+check_taint_not $+, "\t\$+";
+check_taint_not $1, "\t\$1";
+ok($1 eq "\N{CYRILLIC SMALL LETTER A}", ("\t" x 4) . "\t\$1 is 'small cyrillic a'");
+check_taint_not $2, "\t\$2";
+
+/(.)/; # untaint $&, $`, $', $+, $1.
+check_taint_not $&, "\$& from /./";
+
+"(\N{KELVIN SIGN})" =~ /(\N{KELVIN SIGN})/i; # taints because depends on locale
+check_taint $&, "\$& from /(\\N{KELVIN SIGN})/i";
+check_taint $`, "\t\$`";
+check_taint $', "\t\$'";
+check_taint $+, "\t\$+";
+check_taint $1, "\t\$1";
+check_taint_not $2, "\t\$2";
+
+/(.)/; # untaint $&, $`, $', $+, $1.
+check_taint_not $&, "\$& from /(.)/";
+
+"a:" =~ /(.)\b(.)/; # taint $&, $`, $', $+, $1.
+check_taint $&, "\$& from /(.)\\b(.)/";
+check_taint $`, "\t\$`";
+check_taint $', "\t\$'";
+check_taint $+, "\t\$+";
+check_taint $1, "\t\$1";
+check_taint $2, "\t\$2";
+check_taint_not $3, "\t\$3";
+
+/(.)/; # untaint $&, $`, $', $+, $1.
+check_taint_not $&, "\$& from /./";
+
+"aa" =~ /(.)\B(.)/; # taint $&, $`, $', $+, $1.
+check_taint $&, "\$& from /(.)\\B(.)/";
+check_taint $`, "\t\$`";
+check_taint $', "\t\$'";
+check_taint $+, "\t\$+";
+check_taint $1, "\t\$1";
+check_taint $2, "\t\$2";
+check_taint_not $3, "\t\$3";
+
+/(.)/; # untaint $&, $`, $', $+, $1.
+check_taint_not $&, "\$& from /./";
+
+"aaa" =~ /(.).(\1)/i; # notaint because not locale dependent
+check_taint_not $&, "\$ & from /(.).(\\1)/";
+check_taint_not $`, "\t\$`";
+check_taint_not $', "\t\$'";
+check_taint_not $+, "\t\$+";
+check_taint_not $1, "\t\$1";
+check_taint_not $2, "\t\$2";
+check_taint_not $3, "\t\$3";
+
+/(.)/; # untaint $&, $`, $', $+, $1.
+check_taint_not $&, "\$ & from /./";
+