Re^2: syntax of map operator

I since discovered that both versions add a scope.

Yes, but they aren't the same scopes. The EXPR variant doesn't create a lexical scope; the BLOCK variant does:

$ perl -Mstrict -wcE 'my @x = map my $x = $_, 2; say $x'
-e syntax OK
$ perl -Mstrict -wcE 'my @x = map {my $x = $_} 2; say $x'
Global symbol "$x" requires explicit package name at -e line 1.
-e had compilation errors.
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I'm not quite sure what kind of scoping effects happen.

$ perl -Mstrict -wE 'my @x = map my $x = $_, 2; say $x'
Use of uninitialized value $x in say at -e line 1.
$ perl -Mstrict -wE 'my $x; my @x = map $x = $_, 2; say $x'
2
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So, if we declare $x in the first argument of map, $x exists afterwards, but doesn't have a defined value. If declared before the map, it keeps the last assigned value.

I guess that's more an artifact of the implementation than that it was designed to work this way.

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Re^3: syntax of map operator by ikegami (Patriarch) on Jan 24, 2010 at 19:01 UTC
I guess that's more an artifact of the implementation than that it was designed to work this way. I fully agree. Compile-time lexical scopes and run-time lexical scopes should be the same. All of these are in the same bag: `my $x if ...;` `my $x for ...;` `map my $x, ...;` `... and my $;x` Just don't.	[reply] [d/l] [select]
Re^4: syntax of map operator by JavaFan (Canon) on Jan 24, 2010 at 22:48 UTC
I'm very glad `EXPR if COND` doesn't provide a lexical scope. That allows me to write: `local $dbh->{AutoCommit} = 0 if !$already_in_a_transaction;` [download] I once had a cow orker (who thinks he's one of the smartest programmers in the world) rewrite that as `if (!$already_in_a_transaction) { local $dbh->{AutoCommit} = 0; }` [download]	[reply] [d/l] [select]
Re^5: syntax of map operator by Anonymous Monk on Jan 25, 2010 at 04:15 UTC
You should wrap one more `if` around that just to be sure.	[reply] [d/l]