>perl -wMstrict -le
"my %words = map { $_ => 1 } qw($Word $name $test);
 my $line = '$Word $ $ $ $test $testing';
 $line =~ s/(\$(\w*))/exists $words{$1} ? $1 : qq{dollar$2}/eg;
 print $line;
"
$Word dollar dollar dollar $test dollartesting