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Re: while(<>) { ... } considered harmful

by dws (Chancellor)
on Sep 07, 2002 at 23:37 UTC ( #195930=note: print w/ replies, xml ) Need Help??

in reply to while(<>) { ... } considered harmful

Since   map { substr($_, 1, 1) = "foo" } qw(bar baz);
and   grep { substr($_, 1, 1) = "foo" } qw(bar baz);
both exhibit the problem you've observed, perhaps the advice might better be phrased

Don't write to $_ from within map { } or grep { }

local $_; is one way to avoid writing to it, since the 'it' is now different.

Update: Hm.. It's a bit worse than that.   foreach ( qw(foo) ) { $_ = 1 }
also exhibits the problem.

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