If you don't mind predefining your keys:

my $key1 = sprintf "%.2f", 45.20;
my %ITEMS = ( $key1 => 'item 1');
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This will work. I tested it as follows:

$key1 = sprintf "%.2f", 52.30;
my %ITEMS = (
    $key1 => 'item 1',
    45.25 => 'item 2'
);
my $input = <STDIN>;
chomp ($input);
if (exists $ITEMS{$input}) {
    print $ITEMS{$input} . "\n";
}
[download]

It printed "item 1" when I entered 52.30.