Hi Andy,
What does

perl -e '$num=12314212412124124124.10623;print "initial:\t$num\n";prin
+tf ("formatted:\t%f\n",$num);printf ("rounded:\t%.2f\n",$num);'
initial:        1.23142124121241e+19
formatted:      12314212412124123136.000000
rounded:        12314212412124123136.00
[download]

tell you?

that's a very bignum and printf won't handle it

#!/usr/bin/perl
use strict;
use warnings;
use bignum;
sub rounder{
   my ($prec,$num)=@_;
   my $round=0.5 / (10**$prec);
   $num+=$round;
   $num=~ s/(\.\d{$prec})\d*$/$1/;
   return $num;
}
my$num=12314212412124124124.10623;
print "initial:\t$num\n";
print "rounded:\t", rounder(2 ,$num),"\n";
__END__
initial:        12314212412124124124.10623
rounded:        12314212412124124124.11
[download]