What are you trying to do with your code?

I'm just playing around.

Returning a qr// regex is a work around.

I read perlre and re, and I consider "(?{1})" a valid return value. You can use other strings without a problem:

$ id|perl -nle 'print /( (??{ q[uid=\d+] }) )/x'
uid=1000
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This snippet from perlre doesn't specify a regex ref or string (although it is pretty vague). The example which follows in the man page uses a recursive qr// definition (so does return a qr// object).

From perlre:
(??{ code })
... The result of evaluation is considered as a regular expression and matched as if it were inserted instead of this construct.