$screenshots as depicted in $screenshots{$browser} is not an array, it's a hash. So you want to create a hash that contains all of the objects; is that correct?

Here's a very basic example of how you could do this, using a dummy package for testing (I know nothing of Selenium::Screenshot).

use warnings;
use strict;

use Data::Dumper;

package Blah;

sub new {
    my ($class, $browser) = @_;
    return bless {browser => $browser}, $class;
}

package main;

# the example you're interested in is below

my %screenshots;

for my $browser ('ie', 'ff', 'chrome'){
    $screenshots{$browser} = Blah->new($browser);
}

print Dumper \%screenshots;
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Output:

$VAR1 = {
          'ie' => bless( {
                           'browser' => 'ie'
                         }, 'Blah' ),
          'ff' => bless( {
                           'browser' => 'ff'
                         }, 'Blah' ),
          'chrome' => bless( {
                               'browser' => 'chrome'
                             }, 'Blah' )
        };
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