If you need to know how to do the replacement on the string, look at perlre. You could do s/pattern/string/s; but if so, as your pattern match will span multiple lines, you will need the whole file as a single string, which can use up memory on big files.

The alternative is the suggestion by the other poster - run through each line and use a flag to tell you whether you are in a replaceable section.

The more awkward problem is how to replace the text in the file. Again, it is perfectly valid to just open an INPUT filehandle and an OUTPUT filehandle, then to rename the new file to overwrite the old one. However, that is quite complex. A neater idea might be to write a shell script and use some of perl's command line switches. (See perlrun for details.) Something like:

find . -name *.ext -print | xargs perl -pi.bk -e \
'
if ($flag && /end_match/) {$flag = 0;}
if ($flag) {
    $sub = $printed++? '': 'My text to substitute';
    s/^.*$/$sub/;
}
if (/start_match/) {$flag++;$printed = 0;}
'
[download]

That's untested but you get the general idea. Find finds and prints the relevant files. xargs takes the filename and passes it to the end of the perl command. perl reads the filename, prints a copy to filename.bk (you can remove the .bk once you are sure your pattern works), and alters the original file.

No good if you're on windows though...

dave hj~