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

examples/advanced/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