How about this? 

  my $string = 'abcdef 5163 1234 5678';
  my $extracted = $string =~ /(5163(?:\d{8}|\s\d{4}\s\d{4}))/;

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Update: modified code. Thanks davido

In reply to Re: How to write a regular expression to extract a number from an embedded string? by pbeckingham
in thread How to write a regular expression to extract a number from an embedded string? by jwking

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