That introduces problems too. If you try to use sugar like '+' with an implementation that doesn't support it, you don't get any sort of error. Instead you get a different expression.
Unfortunately, there's an inherent tradeoff between encoding efficiency and error detection. Notice that with the VerbalExpressions it would be trivial to return a useful error message if the 'at_least_one' pattern did not exist.
Perl 6 regexes attempt improve upon this situation by making regexes more like a regular programming language. That is it errs on the side of error detection rather than encoding efficiency.
(It also adds features that would be difficult to add to Perl 5/PCRE regex design)
For a start if it didn't support using `+`, then any attempt to use it would generate a compiler error because it is not alphanumeric.
(regex is code in Perl 6)
All non-alphanumeric characters are presumed to be metasyntactic, and so must be escaped in some way to match literally.
Arguably best way is to quote it like a string literal.
(Uses the same domain specific sub-language that the main language uses for string literals)
/ "+" + / # at least one + character
It really is a significant redesign.
/A{2,4}/ # Perl 5/PCRE
/A ** 2..4/ # Perl 6
/A (?:BA){1,3}/x
/A [BA] ** 1..3/ # Perl 6: direct translation
/A ** 2..4 % B/ # Perl 6: 2 to 4 A's separated by B
/A (?:BA){1,3} B?/x
/A ** 2..4 %% B/ # Perl 6: %% allows trailing separator
/\" [^"]* \"/x # Perl 5/PCRE
/\" <-["]>* \"/ # Perl 6: direct translation
/｢"｣ ~ ｢"｣ <-["]>*/ # Perl 6: between two ", match anything else
# (can be used to generate better error messages)
---
# Perl 5
my $foo = qr/foo/;
'abfoo' =~ /ab $foo/x;
# Perl 6
my $foo = /foo/;
'abfoo' ~~ /ab <$foo>/;
# or
my token foo {foo} # treat it as a lexical subroutine
'abfoo' ~~ /ab <&foo>/;
---
# Perl 5
my $foo = 'foo';
'abfoo' =~ /ab \Q $foo \E/x; # treat as string not regex
# Perl 6
my $foo = 'foo';
'abfoo' ~~ /ab $foo/; # that is the default in Perl 6
Unfortunately, there's an inherent tradeoff between encoding efficiency and error detection. Notice that with the VerbalExpressions it would be trivial to return a useful error message if the 'at_least_one' pattern did not exist.