#!/usr/bin/perl -w
use 5.010;
use strict;

print "\n";

my $zahl    = -3.9983629;
my $stellen = 3;

my $rnd = &roundmy ( $zahl, $stellen );
print "Ergebnis $rnd\n";

sub roundmy {

  my $za = shift;

  my $st = shift;

  $za = abs($za);

  my $rest = ( $za =~ /.(\d+)$/ );

  if ( $1 ) {

    my $mult = '1';

    if ( length($1) > $st ) {

      for ( 1..$st ) {

        $mult .= '0'

      }

      my $erg  = int (($za * $mult) + .5) / $mult;

    }

  }

}

print "\n";