I am not sure what the variation in your data can be. For the example given, the following should to the trick.

my $input = '((113000.00 Nos.) + (250000.00 Nos.) ++ (1) )';

$input =~ s/\(|\)| Nos\.//g;
$input =~ s/\+\+/+/g;
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That said, in the long run it probaly will help you to get familiar with regular expressions by reading something like perlre