There was an interesting post on the comp.lang.perl.misc newsgroup regarding this, answered by jwkrahn, the negation has low precedence and needs to be in ()

#!/usr/bin/perl
# http://mathforum.org/library/drmath/view/55721.html

# gives bad output
my $x = ( -1 ** 0 );
print "$x\n";

# correct
my $y = ((-1)**0);
print "$y\n";
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