Exercise: create counter

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Create a script with a function called count() which is capable of maintaining several counters.

examples/advanced-perl/multi-counter-skeleton.pl

#!/usr/bin/perl 
use strict;
use warnings;

print counter('a'), "\n";  # 1
print counter('b'), "\n";  # 1
print counter('a'), "\n";  # 2
print counter('c'), "\n";  # 1
print counter('a'), "\n";  # 3
print counter('a'), "\n";  # 4
print counter('b'), "\n";  # 2