No need to split and grep, just simplify your regex :)

#!/usr/bin/perl

use strict;
use warnings;

my $names = '1Petrus2 Joh4an Smit 2johnny99 Julius 789
  one 2two three3 fo44ur ..5.. six seven, seven7, eight--8--nine ';

while( $names =~ /(\S*\d\S*)/g )
  {
  print "$1\n";
  }
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