Re^3: why not listed foreach and if?

why the restriction?

It's just that perl's parsing does not handle these types of constructs.
It interprets:

foreach @a if $a
as
foreach(@a if $a)
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foreach takes a list as its argument, and I guess perl just doesn't see (@a if $a) as being a valid list.

You know what you mean, and I know what you mean, but perl doesn't.
I don't know exactly why perl doesn't understand these constructs ... but I suspect there are good reasons.

Cheers,
Rob

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Re^4: why not listed foreach and if? by hv (Prior) on Jun 18, 2024 at 00:30 UTC
I'm also not sure why perl doesn't understand them. I suspect they must lead to parsing ambiguities - that usually seems to be the reason for such restrictions. In any case, Perl does not have a history of disallowing things on the grounds of "readability" (that seems much more Python's style). What a person finds readable is very much determined by what they are used to, there really is no single perfect style. Around 25 years ago I was working at Elsevier in Amsterdam, and once had a very heated discussion with the project lead when in code review he wanted to turn my mix of loops and map/grep pipelines (carefully curated so that no single construct was overly complex) into a single much more complex map/grep pipeline that to me seemed totally illegible. My line manager eventually explained that the lead had a functional programming background, and that I should look at the proposed change in that light. It took me a while, but eventually I got my head around it, and I'm now much more comfortable with that style (and find it perfectly legible when done right).	[reply]
Re^5: why not listed foreach and if? by ikegami (Patriarch) on Jun 18, 2024 at 13:37 UTC
Perl does not have a history of disallowing things on the grounds of "readability" Yeah, so it's odd that it's done here. But that was the reason given by Larry Wall (as I remember things). I suspect they must lead to parsing ambiguities Well yeah. Is `X MODA Y MODB Z` equiv to `( X MODA Y ) MODB Z` or `X MODA ( Y MODB Z )`? But that the same applies to every binary operator. These ambiguities are resolved using associativity and precedence.	[reply] [d/l] [select]
Re^4: why not listed foreach and if? by rsFalse (Chaplain) on Feb 01, 2025 at 12:13 UTC
Hi, How you know that perl interprets as `foreach(@a if $A)` but not `(foreach @a) if $A`? I see any of constructs if/for/while can be written inside of parentheses, e.g. a simple `($A if $A)` is a syntax error. 'and' and 'if' internally, as I understand, branch equivalently, only the direction differs. And the result of 'if' becomes not an expression, when the result of 'and' becomes an expression.	[reply] [d/l] [select]