Basic support for -n',-p,-aand-F` options.

• provides access to filename(s) in $ARGV, and current line number (cumulative) in $. (this is kludgy, as a variable with this name could not be created.)
• supports only basic strings for split pattern in -a and -F. When split supports regex patterns, this should work.
• -p behavior is not identical to Perl, as there is continue block to go with while loops.
• I am sure there are other limitations that I haven't thought of.