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;

In reply to Re^2: Compiling Regular Expressions by johndeighan
in thread Compiling Regular Expressions by Anonymous Monk

Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":

  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.