in reply to Re^2: Playing with non-localized $_ in nested loops.
in thread Playing with non-localized $_ in nested loops.

The automatic setting of $_ comes from the combination of while() and readline. Just a plain readline won't do it. Nor does while with just any operator do the implicit assignment.
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Re^4: Playing with non-localized $_ in nested loops.
by davido (Cardinal) on Aug 23, 2004 at 04:36 UTC 
    <DATA>;
print $_;
__DATA__
This is a test.

__OUTPUT__
Use of uninitialized value in print at mytest.pl line 8, <DATA> line 1
+.

    [download]

    Hmm... You're right. There goes that theory. ;) I was erroneously sure that the while() loop's conditional had nothing to do with the fact that the diamond operator feeds $_. Thanks for the enlightenment. :D


    Dave

[reply]
[d/l]
      There are actually two pieces of dwimmery going on; first, if a readline or a glob is the only thing in a while condition (whether a statement modifier or while statement), it gets an implicit $_ =. Next, if a while condition is a scalar assignment from a readline, readdir, glob, or each, the whole condition gets an implicit defined() wrapped around it, so the loop continues on "0" or "".
[reply]
[d/l]

      That is why, in the node you referenced, I was talking about while(<FH>). Invoking the DWIMmery really does require this entire combination of operations.

      Makeshifts last the longest.

[reply]

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