I assume this is *NIX and not Windows?

Your (1) should work if perl is in your PATH, (2) should work if the script has executable permissions and starts with a shebang line appropriate for your system (e.g. "#!/usr/bin/perl" or "#!/usr/bin/env perl"), (3) might work but isn't preferable, the extra slashes don't do anything but add confusion.

However, this isn't a "one liner". A one-liner would be something like perl -e 'print "Hello, World!"' (i.e. the entire program is on the command line and not in a file)

See also Running Perl programs

Please see How do I post a question effectively?: Please show your shell script (wrapped in <code> tags), as well as the error messages you're getting (if any).