How to remove extra line breaks (using regexp)?

larus has asked for the wisdom of the Perl Monks concerning the following question:

Hello, Basic question, probably asked already thousand times, but I could not find a solution for this. I have a file with extra line breaks

A6.8.5 This is 
an example
sentence
A6.8.6 This is 
an example
sentence
[download]

How can I remove those extra line breaks and get each sentence back to original form:

A6.8.5 This is a example sentence
A6.8.6 This is a example sentence
[download]

I have tried something like this:

..snip..
$line =~ s/\r(?!\n)/ /g;
[download]

Comment on How to remove extra line breaks (using regexp)? Select or Download Code

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Re: How to remove extra line breaks (using regexp)? by ikegami (Patriarch) on Apr 17, 2009 at 14:07 UTC
How can you tell which line break to keep so it doesn't turn into `A6.8.5 This is a example sentence A6.8.6 This is a example sentence` [download] Will the line always start with `/A\d+\./`?	[reply] [d/l] [select]
Re^2: How to remove extra line breaks (using regexp)? by larus (Acolyte) on Apr 17, 2009 at 14:12 UTC
Well, yeah, that is the problem. There is other shitty thing also in this .txt file that I'm trying to clean but basically the lines that I want to keep starts with a letter and a digit.	[reply]
Re^3: How to remove extra line breaks (using regexp)? by ikegami (Patriarch) on Apr 17, 2009 at 14:40 UTC
`my $file = do { local $/; <DATA> }; $file =~ s/\n(?!A\d+\.)/ /g; $file .= "\n"; print $file; __DATA__ A6.8.5 This is an example sentence A6.8.6 This is an example sentence` [download] `A6.8.5 This is an example sentence A6.8.6 This is an example sentence` [download]	[reply] [d/l] [select]
Re^4: How to remove extra line breaks (using regexp)? by Anonymous Monk on Apr 17, 2009 at 15:15 UTC
Re: How to remove extra line breaks (using regexp)? by bichonfrise74 (Vicar) on Apr 18, 2009 at 05:18 UTC
Would this work? `#!/usr/bin/perl use strict; my @file = <DATA>; foreach my $i (@file) { $i =~ s/\n/ /; $i =~ /^A\d\.\d\./ ? print "\n$i" : print $i; } __DATA__ A6.8.5 This is an example sentence A6.8.6 This is an example sentence` [download]	[reply] [d/l]
Re^2: How to remove extra line breaks (using regexp)? by Anonymous Monk on Apr 18, 2009 at 07:39 UTC
yes, it works, thanks	[reply]