Then plz show your efforts in using them.

Comparison of strings such as filenames should use the cmp operator which will return -1, 0 or +1 to show which value comes first.
Comparison of numerical values should use <=> which will also return -1, 0 or +1 to show which value is bigger.

Zero meaning the two values are equal, of course

It would have been nice if you showed what you tried, but here's a pretty simplistic way to do what you want:

#!/usr/bin/perl

use warnings;
use strict;
use 5.12.0;

my %h1 = ( a => 1, b => 2, c => 3, e => 5, );
my %h2 = ( a => 2, b => 2, d => 4, e => 5, );

my @filenames;

while ( my ( $k, $v ) = each %h1 ) {
    if ( exists $h2{ $k } ) {
        push @filenames, $k if $v == $h2{ $k };
    }
}

say "$_" for @filenames;
[download]

Steve

#!/usr/bin/perl
use warnings;
use strict;
use feature qw(say);

my %size1 = ( 'autorun.inf'  =>  42,
              'autoexec.bat' => 118,
              'eicar.zip'    => 186,
            );

my %size2 = ( 'autorun.inf'  =>     42,
              'autoexec.bat' =>    119,
              'ibmbio.com'   => 234186,
            );

my %files;
undef @files{keys %size1, keys %size2};

for my $file (keys %files) {
    delete $files{$file}, next if exists $size1{$file}
                              and exists $size2{$file}
                              and $size1{$file} == $size2{$file};
    $files{$file} = 'Missing in 1', next unless exists $size1{$file};
    $files{$file} = 'Missing in 2', next unless exists $size2{$file};
    $files{$file} = 'Size changed';
}

for my $file (keys %files) {
    say "$file\t$files{$file}";
}
[download]

Test::Deep::NoTest is a good tool for comparing data structures.