If I understand the documentation, you can remove eval from there, as it's useless for qr{}.

Well, as far as I can tell, the code the OP posted doesn't make use of the eval feature at all , the code section is a literal

literal

$ perl -E " $_ = 123; m/\d(?{ warn pos })/"
1 at (re_eval 5) line 1.

$ perl -E " no re qw/eval/; $_ = 123; m/\d(?{ warn pos })/"
1 at (re_eval 5) line 1.

$ perl -E " $_ = 123; $f = qr/\d(?{ warn pos })/; m/$f/;"
1 at (re_eval 5) line 1.

$ perl -E " no re qw/eval/; $_ = 123; $f = qr/\d(?{ warn pos })/; m/$f
+/;"
1 at (re_eval 5) line 1.
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variable aka "dynamic" aka it throws error :)

$ perl -E " $_ = 123; $f = '(?{ warn pos })';  m/\d$f/; "
Eval-group not allowed at runtime, use re 'eval' in regex m/\d(?{ warn
+ pos })/ at -e line 1.

$ perl -E " $_ = 123; $f = '(?{ warn pos })';  $g = qr/\d$f/; m/$g/"
Eval-group not allowed at runtime, use re 'eval' in regex m/\d(?{ warn
+ pos })/ at -e line 1.
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I believe whatever the OPs real code, he got this error message so he added the "solution"

I also believe there is no need for any of this stuff :) if all the OP is doing is building a data structure, simply match in a loop and use %+ or use Regexp::Grammars