We can load the file into an array, loop through the array incrementing a hash using the entry as the key. Then loop through the hash sorted printing the value and the key.

use strict;
use warnings;

my @lines = <DATA>;
chomp @lines;

my $saw = {};
$saw->{$_}++ foreach @lines;

print "$saw->{$_} = $_\n" foreach sort keys %$saw;

__DATA__
a
b
va
sdf
b
a
v
b
n
a
h
[download]

Produces:

3 = a
3 = b
1 = h
1 = n
1 = sdf
1 = v
1 = va
[download]