I'd go the other way - converting the int to a string.

use strict;
use warnings;

use Data::Dumper;
use Test::More tests => 1;

my $num1 = 1990;
my $num2 = '19.90';

$num1 = sprintf ("%.2f", $num1 * 0.01);

is $num1, $num2;

diag Dumper ([$num1, $num2]);
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