Re: Beginner question about search and replace

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;
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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

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Re^2: Beginner question about search and replace by hilbert (Acolyte) on Sep 16, 2011 at 11:47 UTC
Thanks a lot for your absolutely clear explanation and solution.	[reply]
Re^2: Beginner question about search and replace by Anonymous Monk on Sep 16, 2011 at 17:36 UTC
You may also wish to note that if you're reading the data from a file and don't chomp the trailing newline, the two versions will produce different results. The first form will result in a trailing ';' because newline is part of the whitespace character class. (\s) -Greg	[reply]