Re^2: Replace first blank line in a text file with headers.

Those changes won't work anyway as the code stands, because the OP code is opening the same file twice, once in read mode and once in write mode. That's a no-go.

The Tie::File module is a solution, a one-liner using in-line option is another. Else, opening another file for writing, making the necessary changes, and renaming the files is another option.

Then only should we worry about avoiding to change other lines, one way or another.

Comment on Re^2: Replace first blank line in a text file with headers.

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Re^3: Replace first blank line in a text file with headers. by Marshall (Canon) on Mar 24, 2016 at 23:04 UTC
I would have some code to make a backup of some kind, even if I used Tie::File. There is just so much that can go wrong when debugging a new version or some slightly different input file shows up and program fails. I've saved my own butt many times with a .bak1, .bak2 file...This stuff can go in a temp directory that periodically gets cleaned out. Creating long lived "junk" is also a problem, but of a different sort. If you have backups from yesterday that's a good thing, but I never want to resort to that to fix something that just went wrong 5 minutes ago.	[reply]
Re^3: Replace first blank line in a text file with headers. by ExReg (Priest) on Mar 24, 2016 at 19:52 UTC
Too true.	[reply]
Re^4: Replace first blank line in a text file with headers. by rementis (Beadle) on Mar 24, 2016 at 21:22 UTC
Should be pretty easy. Just open a new output file, print your header to it. Then cycle through your input file, skipping all blank lines. Then close your output file.	[reply]