Question: The one-liner should:

* solve a real-world problem
* not be extensively cryptic (should be easy to understand and reproduce)
* be worth the time it takes to write it (should not be too clever)

I'm looking for practical tips and tricks (complementary examples for `perldoc perlrun`).

Answer: 
Please see my slides for ["A Field Guide To The Perl Command Line Options."](https://web.archive.org/web/20120916013412/http://petdance.com/perl/command-line-options.pdf)
Expand all tabs to spaces: `perl -pe'1while+s/\t/" "x(8-pos()%8)/e'`

Of course, this could be done with :set et, :ret in Vim.