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use strict;
use warnings;

my $data = <<DATA;
Some sample text with the odd ',', '.', '[', ']' and '-'
as test input.
DATA

open my $inFile, '<', \$data;

my %hits;
while (<$inFile>) {
    ++$hits{$_} for split '';
}

print "$_: $hits{$_}\n" for ',', '.', '[', ']', '-';
[download]

Prints:

,: 4
.: 2
[: 1
]: 1
-: 1
[download]