Re^2: Help with multiple line regex subsitution

The s modifier might help you.

The //s regex modifier would not seem helpful since it modifies the behavior of the . (dot) regex metacharacter, and this metacharacter is used in neither the OP nor in your reply.

The OPer seems to be looking for a simple way to get the contents of the file as a single string. A simple way to do this is with the idiomatic statement
my $string = do { local $/; <$fh> }
(where $fh is an already-opened file handle). After modification, this string can be printed with a single print statement. Caution: this approach does not scale well to files of more than several megabytes (depending on your system's memory).

Also, the following regex accepts only balanced double-quotes on the "string" and requires the trailing '{' character.

>perl -wMstrict -le
"my $s = join '', @ARGV;
 $s = eval qq[qq[$s]];
 my $words = qr{ foo | bar }xms;
 $s =~ s{ (Kw \s+) (\"?) ($words) (\2 \s* \{) }{$1${2}1_$3$4}xmsg;
 print 'output:';
 print $s;
"
"Kw \n foo \n { \n Kw \n \"bar\"\n { \n Kw foo { Kw \"foo\" { "
"Kw \"foo { Kw foo\" { Kw foo Kw {"
output:
Kw
 1_foo
 {
 Kw
 "1_bar"
 {
 Kw 1_foo { Kw "1_foo" { Kw "foo { Kw foo" { Kw foo Kw {
[download]

Updates:

The //g modifier which you use in your reply is, however, critical in a single-string solution!
Added regex solution.

Comment on Re^2: Help with multiple line regex subsitution Select or Download Code

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Re^3: Help with multiple line regex subsitution by Porculus (Hermit) on Apr 14, 2009 at 22:18 UTC
Caution: this approach does not scale well to files of more than several megabytes (depending on your system's memory). In the unlikely case that this is a problem, it's fairly straightforward to switch to reading blocks rather than slurping the entire file in one go. You just have to remember to handle the case where a sequence you want to match is split across a block boundary, and that's just a case of checking to see if the last part of the block could possibly be a prefix of a matching sequence, and if it could, then prepending it to the next block you read. (Implementing this is left as an exercise for someone in a time zone where it's earlier in the day.) But it's really very unlikely that this will be a problem. A file with a format like that is unlikely to reach even one megabyte -- if it does, then either it should have been split up into multiple files long ago (if it's intended for human reading and writing); or it should be being stored in a standard format like XML or JSON, and transformed with a standard library, not regular expressions.	[reply]
Re^4: Help with multiple line regex subsitution by AnomalousMonk (Archbishop) on Apr 15, 2009 at 16:43 UTC
In the unlikely case that this is a problem, it's fairly straightforward to switch ... I think we are not so far apart on this. Switching involves abandoning one approach to solving the problem (and I might more clearly have expressed the idea that 'this approach' meant 'read the entire file to a string, operate on the string, and write the string back to a file') for a significantly different approach, perhaps one of those outlined in the balance of your reply. This is what I mean when I write that the approach does not scale well. I agree that, given what one can divine about the OPer's data from the OP, the problem is not likely to arise. In fact, I would go further and say that, in my experience, problems like this never happen – until they happen, and then you have to go back and change a bunch of stuff and re-test everything; which, while straightforward, still costs time, effort and risk; hence, the caution about lack of scalability.	[reply]