use strict;
use warnings;

my $num1 = 2.3;
print "$num1 -> ";
$num1 =~ s/\./.0/;
print "$num1\n";

$num1 = 2.3;
print "$num1 -> ";
$num1 =~ s/(?<=\d\.)(?=\d)/0/;
print "$num1\n";

__DATA__
2.3 -> 2.03
2.3 -> 2.03