I want to know when 
while (<>) {
}

[download]
has something available to read. I'd like to not execute this code when there isn't something available because it will block.

This idiom will read when @ARGV is populated or when there is some data available to read on STDIN.

I can handle detecting whether @ARGV has data. What I'm not sure on is how to detect whether STDIN has something available to read. Still testing but I'm not convinced, yet, that -t, as suggested by others, will work here.

In reply to Re^2: detect input available from command line by mifflin
in thread detect input available from command line by mifflin

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