You can simply #2 a a bit: 

$rx_4333 = /(?=\d{4}$)
   (?: 4     (?: 3     (?: 3     [3-9]
                       |   [4-9]
                       )
             |   [4-9]
             )
   |   [5-9]
   )
$/x

[download]
That rx can be built dynamically as follows: 
my @digits = $ProdBuild =~ /([0-9])([0-9])([0-9])([0-9])$/;

my $rx = '(?=\\d{4}$)';
for (@digits) {
   $rx .= "(?:$_";
}
for (reverse @digits) {
   local $_ = $_+1;
   $rx .= '|' . ($_ == 9 ? 9 : "[$_-9]") if $_ != 10;
   $rx .= ')';
}

# 4333 gives (?=\d{4}$)(?:4(?:3(?:3(?:3|[4-9])|[4-9])|[4-9])|[5-9])

foreach (@pattern) {
   print("Match: $_\n") if /$rx/;
}

[download]

Update: I cleaned up the regexp building code a bit, at the cost of a little redundancy in the regexp. For example, a last digit of 3 results in 3|[4-9].

In reply to Re^2: Regular expression patter matching question by ikegami
in thread Regular expression pattern matching question by ramya2005

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