First let me explain why your solution doesn't work as expected:

s///g starts each match where the previous match left off, or at the start of the string for the first match.

The first match finds 1 2, and the next match searches for a \d, which is the 3 -- no overlap occurs.

A possible fix is to not match the second digit: 

s/(\d)\s+/$1;/g;

[download]

Which produces the output you want. If it's important that no substitution happens after a number but before a letter, you can use 

s/(\d)\s+(?=\d)/$1;/g;

[download]

The (?=\d) looks for a digit, but it doesn't consume it (search for look-ahead in perlre).

Update: Kudos for supplying your code, actual output and expected output. It makes answering your question easy, and can't be taken for granted. Welcome to perlmonks!

Perl 6 - second systems done right

In reply to Re: Beginner question about search and replace by moritz
in thread Beginner question about search and replace by hilbert

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