STDIN is always there.

Maybe you want to detect instead of whether your script is supposed to get interactive input or input piped from a file, or another program?

if( -t and !@ARGV) {
    die "Need a file or stream on standard input";
};

while (<>) {
    ...
};

[download]
>perl -w tmp.pl
Need a file or stream on standard input at tmp.pl line 2.

>perl -w tmp.pl tmp.pl

>perl -w tmp.pl <tmp.pl

[download]

In reply to Re: Testing <> by Corion
in thread Testing <> by Anonymous Monk

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