use strict;

my $number = 12650 / 10000;
#my $number = 1.265;
my $dp = 2;

print "Actual: $number\n";


my $exp = 10 ** ($dp);

my $val1 = int(($number * $exp) * 10);
my $val2 = $val1 + 5;
my $val3 = int($val2/10);
my $val4 = $val3 / $exp;

print "$val1\n";
print "$val2\n";
print "$val3\n";
print "$val4\n";

output

Actual: 1.265
1264
1269
126
1.26


rem out the 1265/1000
an unrem out the 1265

output

Actual: 1.265
1265
1270
127
1.27