Add blank line between two consecutive lines starting with specified strings

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

I have a file which may include consecutive lines like this
\macroa xxxx (rest of line)
\macrob xxxx (rest of line)

I want to replace all such pairs with
\macroa xxxx (rest of line)
(blank line here)
\macrob xxxx (rest of line)

Is this possible with a perl one-liner?

Thank you.

Comment on Add blank line between two consecutive lines starting with specified strings

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Re: Add black line between two consecutive lines starting with specified strings by AnomalousMonk (Archbishop) on Feb 10, 2018 at 02:31 UTC
It is certainly possible. Assuming Windows command line (update: and assuming "black" means "blank"), try (semi-tested): `perl -wMstrict -pe "BEGIN { our $armed } $::armed = /\A \\macroa \s/x +? 1 : /\A \\macrob \s/x && $::armed && ! print qq{\n}" infile > outfi +le` [download] Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re^2: Add blank line between two consecutive lines starting with specified strings by texuser (Novice) on Feb 10, 2018 at 05:02 UTC
Thank you, it works.	[reply]
Re^3: Add blank line between two consecutive lines starting with specified strings by AnomalousMonk (Archbishop) on Feb 10, 2018 at 06:33 UTC
I'm glad it works, and you're welcome. Do you understand why it works? We do not aspire to be a code-writing service. Evidence of effort on your part will beget effort on ours. Looking at your admittedly limited posting history ... Give a man a fish: `<%-{-{-{-<`	[reply] [d/l]
Re^4: Add blank line between two consecutive lines starting with specified strings by texuser (Novice) on Feb 10, 2018 at 09:59 UTC
Re^5: Add blank line between two consecutive lines starting with specified strings by Marshall (Canon) on Feb 10, 2018 at 18:51 UTC