The issue is not that it's lexical, but that assigning to a lexical $_ instead of the superglobal $_ broke assumptions that people make that $_ can be used in other code scopes dynamically, such as subroutines you call. If it had started out being lexically aliased by foreach and map it would lead to safer code overall.
local assignment does avoid some danger of action at a distance from aliasing with foreach; in the following code, if some_sub were to assign anything to $_ it would clobber $var as well.
my$var='foo';foreach($var){some_subandlast;}
In the end I always recommend using a few more keystrokes and avoiding $_ for this entirely.
I whipped up two quick tests: gist.github.com/matthewpersico/aa1... and gist.github.com/matthewpersico/aa1... and yes, not having that local can be disastrous. So, since for and map and the like are coded "properly", i.e., they localize $_, you should be safe to use them and use functions that call them. But if someone has done this $_ assignment trick and forgets the local, there be dragons.
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The issue is not that it's lexical, but that assigning to a lexical
$_instead of the superglobal$_broke assumptions that people make that$_can be used in other code scopes dynamically, such as subroutines you call. If it had started out being lexically aliased byforeachandmapit would lead to safer code overall.localassignment does avoid some danger of action at a distance from aliasing withforeach; in the following code, if some_sub were to assign anything to$_it would clobber$varas well.In the end I always recommend using a few more keystrokes and avoiding
$_for this entirely.I whipped up two quick tests:
gist.github.com/matthewpersico/aa1... and gist.github.com/matthewpersico/aa1... and yes, not having that
localcan be disastrous. So, sinceforandmapand the like are coded "properly", i.e., theylocalize$_, you should be safe to use them and use functions that call them. But if someone has done this$_assignment trick and forgets thelocal, there be dragons.