What is Perl one-liner?

There are two ways a Perl script can be run:

a)from a command line, called one-liner, that means you type and execute immediately on the command line. You'll need the -e option to start like "perl -e "print "Hello";". One-liner doesn't mean one Perl statement. One-liner may contain many statements in one line.

b)from a script file, called Perl program.