A typical approach is to have a flag which indicates if you currently need you write to an output-file or not.

Just read the input-file line-by-line and determine one of the following four situations:

• You find the start-pattern: now open a new output file based on the number inside the pattern (hint: use a regex). And set your flag
• You find the end-pattern: just close your output-file and reset the flag
• You find any other line and the flag is set: write that line to your output-file
• You find any other line and the flag is not set: ignore that line

Of course you might want to add some error-checking, too!

Have fun implementing! If you encounter any Perl-questions, feel free to show your code and where you have issues, so we monks can give you further advice

HTH, Rata