Have you tried this: 
my_script 'my\narg\nwith\nline\nbreaks'

...
$ARGV[0] =~ s/\\n/\n/g;
...

[download]
(update: actually, you could use any distinctive character or pattern of your choosing to serve as a placeholder for line breaks -- just be clear about it in your "Usage: ..." synopsis and/or man page, and do the appropriate regex replacement as the first thing in the script.)

In reply to Re: How to keep the line breaks in the arguments when I invoke Perl? by graff
in thread How to keep the line breaks in the arguments when I invoke Perl? by henrycui

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