$ cat infile1.txt
line1
line3
line2
line1
line3
line4
line2

##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my %hash;
my $myfile = '/dir/subdir/infile1.txt'; 

open( my $in, '<', $myfile) or die "Can't open $myfile: $!"; 
map { chomp; $hash{ $_ }++ } <IN>;
close($in);
print Dumper \%hash;

##</code><code>##

Output:
$VAR1 = {
          'line3' => 2,
          'line2' => 2,
          'line4' => 1,
          'line1' => 2
        };