# reproduction
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$ rot13
Command 'rot13' not found, but can be installed with:
sudo apt install hxtools
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$ sudo apt install hxtools
[sudo] password for <your_UID>
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# Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
  libhx32
The following NEW packages will be installed:
  hxtools libhx32
0 upgraded, 2 newly installed, 0 to remove and 5 not upgraded.
Need to get 181 kB of archives.
After this operation, 692 kB of additional disk space will be used.
Do you want to continue? [Y/n]
Get:1 http://deb.debian.org/debian bookworm/main amd64 libhx32 amd64 4.10-1 [38.9 kB]
Get:2 http://deb.debian.org/debian bookworm/main amd64 hxtools amd64 20221119-1 [142 kB]
Fetched 181 kB in 1s (197 kB/s)
Selecting previously unselected package libhx32:amd64.
(Reading database ... 375257 files and directories currently installed.)
Preparing to unpack .../libhx32_4.10-1_amd64.deb ...
Unpacking libhx32:amd64 (4.10-1) ...
Selecting previously unselected package hxtools.
Preparing to unpack .../hxtools_20221119-1_amd64.deb ...
Unpacking hxtools (20221119-1) ...
Setting up libhx32:amd64 (4.10-1) ...
Setting up hxtools (20221119-1) ...
Processing triggers for man-db (2.11.2-2) ...
Processing triggers for libc-bin (2.36-9+deb12u9) ...
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$ vim.athena rot_gag.nfo
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$ man rot13
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# rot13(1)                                          hxtools                                          rot13(1)

Name
       rot13 — shortcut to tr(1) for ROT13

Syntax
       rot13 [file...]

Description
       ROT13  ("rotate  by  13 places", sometimes hyphenated ROT-13) is a simple letter substitution cipher
       that replaces a letter with the letter 13 letters after it in the Latin alphabet.

       rot13(1) will call out to tr(1) to do this substitution, and will read from  standard  input  unless
       some filenames are given.

See also
       hxtools(7)

hxtools                                          2013-08-02                                        rot13(1)
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$ rot13 rot_gag.nfo