You'll only get the extra info if the filehandle read from is still open. closing the file (ARGV in the case of the diamond operator) switches it off again. 

P:\test>echo "" | perl -wle "<>; warn 'Erk!'"
Erk! at -e line 1, <> line 1.

P:\test>echo "" | perl -wle "<>; close ARGV; warn 'Erk!'"
Erk! at -e line 1.

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Explicitly closing DATA once the loop completes is useful sometimes.

Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"Think for yourself!" - Abigail
"Memory, processor, disk in that order on the hardware side. Algorithm, algorithm, algorithm on the code side." - tachyon

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

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