Allow multivariable foreach to use refaliases#24094
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leonerd merged 5 commits intoPerl:bleadfrom Jan 22, 2026
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New helper functions to avoid some copy-paste. Also because I'm otherwise about to add a third copy.
Currently these are all scalar variables, but soon I will add the ability for iteration variables to be refaliases, so they won't necessarily all be scalars any more.
* Define a new private op constant OPpITER_REFALIAS * Presence of this flag on OP_ITER means the iteration var is a refalias * Throw away the LVREF/REFGEN part of the optree in favour of just setting this flag This change is useful on its own, and also a good stepping-stone towards being able to implement multiple refalias variables in foreach; as per Perl#24027
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As noted by Perl#24027, while multivar foreach and refalias foreach have each been available separately for some time now, it wasn't possible to combine the two until now. This current implementation does have limits on the number of variables in total are allowed in a multivariable foreach loop if any are refaliases (no more than 256), and which ones can be refaliases (none past the 24th) that are all to do with the way I am abusing the U32 `op_targ` field to store the variable count in the lower 8 bits, and a bitmask of which vars are refaliases in the upper 24 bits. I decided to do that as it means I don't have to make the `OP_ITER` op any larger - such as by expanding it to an UNOP_AUX to give it that extra storage space. In practice I don't imagine those limits will be a problem for any practical use-case. If in a future version we did want to expand on those limits, I think it would be possible by moving the `refalias_mask` storage to a PV stored in the UNOP_AUX vector, or somesuch.
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tonycoz
approved these changes
Jan 21, 2026
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Fixes #24027
As noted by #24027, while multivar foreach and refalias foreach have each been available separately for some time now, it wasn't possible to combine the two until now.
This current implementation does have limits on the number of variables in total are allowed in a multivariable foreach loop if any are refaliases (no more than 256), and which ones can be refaliases (none past the 24th) that are all to do with the way I am abusing the U32
op_targfield to store the variable count in the lower 8 bits, and a bitmask of which vars are refaliases in the upper 24 bits. I decided to do that as it means I don't have to make theOP_ITERop any larger - such as by expanding it to an UNOP_AUX to give it that extra storage space. In practice I don't imagine those limits will be a problem for any practical use-case.If in a future version we did want to expand on those limits, I think it would be possible by moving the
refalias_maskstorage to a PV stored in the UNOP_AUX vector, or somesuch.