/usr/share/doc/xmlstarlet/examples/sel-if is in xmlstarlet 1.6.1-2.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 | #!/bin/sh
echo '<x/>' | ./xmlstarlet sel -T -t -i 'true()' -o yes -n --else -o no -n -b -o all -n
echo '<x/>' | ./xmlstarlet sel -T -t -i 'false()' -o yes -n --else -o no -n -b -o all -n
echo '<x/>' | ./xmlstarlet sel -T -t -i 'false()' -o yes -n --elif 'true()' -o maybe -n --else -o no -n -b -o all -n
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