The following one-liner would do it. (Wrapped for posting. Quotes are shell dependant.) 

perl 
-nwle"/bn(\d{4})/ && $1 >= 4000 && $1 <=6200 && ++$c{ $1 };" 
-e"END{ print qq[$_ => $c{ $_ }] for sort keys %c}" temp.dat

4370 => 1
4512 => 1
5600 => 2
6042 => 1
6085 => 2

[download]
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re: Parsing a Flat File and counting occurances of numbers? by BrowserUk
in thread Parsing a Flat File and counting occurances of numbers? by batcater98

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