I noticed that the behavior was consistant for filehandle reads, which is why I found the behavior of globbing perplexing...

The following lines are equivalent to each other: 

while (<STDIN>) { print; }      # tests for definedness
print while <STDIN>;            # tests for definedness

[download]
But these two are not equivalent to each other: 
while ($_ = <*>) { print }      # tests for definedness
print while ($_ = <*>);         # tests for truthfulness

[download]
Update -- Here is an example in action: 
% mkdir newdir
% cd newdir
% touch 0 1 2
% ls
0  1  2

% perl -le 'while ($_ = <*>) { print }'
0
1
2

% perl -le 'print while ($_ = <*>)'     
[note nothing is printed here]

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-Blake

In reply to Re4: When does while() test for defined vs truth by blakem
in thread When does while() test for defined vs truth by blakem

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