I want to embed Perl code in my regex using (?{...}), so it's critical that the regex is compiled at compile time. I've gotten this to work without errors or warnings:
my $kind;
my $REGEX = qr/
[A-Za-z][\w]* (?{$kind = 'IDENT';})
| (?: ==? | != | <=? | >=? ) (?{$kind = 'OP';})
| -?\d+ (?{$kind = 'INT';})
| \x27 ( (?:[^\x27] | \x27{2})* ) \x27 (?{$kind = 'STRING';})
| \S (?{$kind = 'OTHER';})
/xs;
However, I'd like to better organize the regex by splitting it into parts, then using those parts. This is what I'd like to do, but when I try, I get the error "Eval-group not allowed at runtime, use re 'eval' in regex". I think that the suggested workaround is bad practice, so I won't do it, but I don't understand why what I'm trying to do won't work since all the regex's involved use qr//. I've also tried using Readonly for the parts, but Perl still doesn't recognize that the parts I'm using will never change. Is there any other way to get $REGEX to compile at compile time while breaking it into parts?
my $IDENT = qr/ [A-Za-z][\w]* /xs;
my $STRING = qr/ \x27 ( (?:[^\x27] | \x27{2})* ) \x27 /xs;
my $OP = qr/ (?: ==? | != | <=? | >=? ) /xs;
my $INT = qr/ -?\d+ /xs;
my $kind;
my $REGEX = qr/
$IDENT (?{$kind = 'IDENT';})
| $OP (?{$kind = 'OP';})
| $INT (?{$kind = 'INT';})
| $STRING (?{$kind = 'STRING';})
| \S (?{$kind = 'OTHER';})
/xs;