Wishful thinking must die...

my $sentence="to baah or not to chomp, that's the question";

my $garbage = 0;
$garbage++ while ($sentence =~ /[,'\s]/g);
@chars = split //, $sentence;
print "You can create ", (scalar(@chars) - $garbage)/4.0," groups of f
+our characters here\n";
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A little twisted but it works... note that you don't lose any info here in your sentence

Updated: printing the groups

@chars = grep {!/(,|'|\s)/} @chars;
my $n = 0;
while ($n < $#chars){
  print $chars[$n],$chars[$n+1],$chars[$n+2],$chars[$n+3],"\n";
  $n = $n+4}
[download]