It seems like the doc is incomplete with regard to the dash character:
The => operator is a synonym for the comma except that it causes its left operand to be interpreted as a string if it begins with a letter or underscore and is composed only of letters, digits and underscores. This includes operands that might otherwise be interpreted as operators, constants, single number v-strings or function calls. If in doubt about this behavior, the left operand can be quoted explicitly.

=> treats the dash as a string, although the doc does not mention it: 

use warnings;
use strict;
use Data::Dumper;

my %h = (-v => 5);
print Dumper(\%h);
print "$h{-v}\n";

__END__

$VAR1 = {
          '-v' => 5
        };
5

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In reply to Re^2: Understanding arguments to subroutines by toolic
in thread Understanding arguments to subroutines by uday_sagar

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