When I run this code using Perl v5.14.2 on Ubuntu: 

#! /usr/bin/perl
use strict;
use warnings;
$_ = 42;
printf "%d\n";

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I get: Missing argument in printf at ./p line 5.

However, perldoc -f printf says that it should work:

printf FILEHANDLE FORMAT, LIST
printf FILEHANDLE
printf FORMAT, LIST
printf
...
If you omit the LIST, $_ is used;

In reply to $_ as default printf arg fails by Neutron Jack

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