Many oneliners rely on the magic of Perl's -i switch, which means when files supplied on the commandline are opened they are edited in place, and if an extension was passed, a backup copy with that extension will be made. -e specifies the Perl code to run. See perlrun(1) for any other switches used here - in particular, -n and -p make powerful allies for -i.
The unsurpassed power of Perl's RegularExpression flavour contributes a great deal to the usefulness of nearly every oneliner, so you will also want to read the perlretut(1) and perlre(1) manpages to learn about it.
perl -ni.bak -e'/\S/ && print' file1 file2
perl -00 -pi.bak -e1 file1 file2
Note the use of 1 as a no-op piece of Perl code. In this case, the -00 and -p switches already do all the work, so only a dummy needs to be supplied.
perl -e 'printf "%08b\n", $_ for unpack "C*", shift' 'My String'
cat $file | perl -ne 's/\\n/\012/g; s/\\t/\011/g; print'
You can use any punctuation as the separator in an s/// command, and if you have backslashes or even need literal slashes in your pattern then doing this can increase clarity.
4 pages link to PerlOneLiners: