my %data = (
  ma_test => 1,
  mb_test => 'the RTE',
);
my $text = 'titl=This is test $ma_test blah $x of $mb_test broadcasting system';
$text =~ s/\$(\w+)/ exists $data{lc $1} ? $data{lc $1} : '==VARIABLE_NOT_FOUND==' /eg;
print $text;