print $RE{delimited}{-delim => 'ab'};

##</code><code>##

(?:(?|(?:a)(?:[^\\a]*(?:\\.[^\\a]*)*)(?:a)|(?:b)(?:[^\\b]*(?:\\.[^\\b]*)*)(?:b)))

##</code><code>##

print $RE{delimited}{-delim => '[\\\/]'};

##</code><code>##

(?:(?|(?:\[)(?:[^\\\[]*(?:\\.[^\\\[]*)*)(?:\[)|(?:\\)(?:[^\\]*(?:(?:\\\\)[^\\]*)*)(?:\\)|(?:\\)(?:[^\\]*(?:(?:\\\\)[^\\]*)*)(?:\\)|(?:\/)(?:[^\\\/]*(?:\\.[^\\\/]*)*)(?:\/)|(?:\])(?:[^\\\]]*(?:\\.[^\\\]]*)*)(?:\])))

##</code><code>##

print qr'a';
print "\n\n";
print $RE{delimited}{-delim => qr'a'};
print "\n";

##</code><code>##

(?^:a)

(?:(?|(?:\()(?:[^\\\(]*(?:\\.[^\\\(]*)*)(?:\()|(?:\?)(?:[^\\\?]*(?:\\.[^\\\?]*)*)(?:\?)|(?:\^)(?:[^\\\^]*(?:\\.[^\\\^]*)*)(?:\^)|(?:\:)(?:[^\\\:]*(?:\\.[^\\\:]*)*)(?:\:)|(?:a)(?:[^\\a]*(?:\\.[^\\a]*)*)(?:a)|(?:\))(?:[^\\\)]*(?:\\.[^\\\)]*)*)(?:\))))