Data::Dumper prints it for me (Perl 5.8.8, Solaris): 
perl -MData::Dumper -e '$_ = "\x00" x 4; print Dumper $_' | cat -v
$VAR1 = '^@^@^@^@';

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In reply to Re^2: the repetition operator does not repeat "\x00" Why? by djp
in thread the repetition operator does not repeat "\x00" Why? by borisz

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