Append n number of 0's as the prefix of integer

Question

I have the following data in a CSV file.

2454,"dum my"
12345,"dummy"
300001,"du m m y"

I was wondering, what regular expression I can use, to turn them into

002454,"dummy"
012345,"dummy"
300001,"dummy"

Thanks.

Answer 1

I'd recommend reading and rewriting the CSV file with Text::CSV_XS and manipulating the fields individually, but if you must just use a regex, something like:

sub strip_spaces { my $str = shift; $str =~ y/ //d; $str }
s/(\d+)/ sprintf '%.6d', $1 /e;
s/("[^"]+"$)/ strip_spaces($1) /e;