See perldoc -f -X:

my $loglevel;

$loglevel++ if -t STDOUT;

print "Log level is $loglevel\n";

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This will not work if the user is running your program through less or any other pager I guess.

In reply to Re: How to tell whether script is invoked from command line or not by Corion
in thread How to tell whether script is invoked from command line or not by theguvnor

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