pl - Swiss Army Knife of Perl One-Liners

Just one small self-contained script extends "perl -E" with many bells &
whistles: Various one-letter commands & magic variables (with meaningful
aliases too) and more nifty loop options take Perl programming to the command
line.  List::Util is fully imported.  If you pass no program on the command
line, starts a simple Perl Shell.

How to "e(cho)" values, including from "@A(RGV)", with single "$q(uote)" &
double "$Q(uote)".  Same for hard-to-print values:

    pl 'echo "${quote}Perl$quote", "$Quote@ARGV$Quote"' one liner
    pl 'e "${q}Perl$q", "$Q@A$Q"' one liner

    pl 'echo \"Perl", \@ARGV, undef' one liner
    pl 'e \"Perl", \@A, undef' one liner

Print up to 3 matching lines, resetting count (and "$.") for each file:

    pl -rP3 '/Perl.*one.*liner/' file1 file2 file3

Loop over args, printing each with line ending.  And same, shouting:

    pl -opl '' Perl one liner
    pl -opl '$_ = uc' Perl one liner

Count hits in magic statistics hash "%n(umber)":

    pl -n '++$n{$1} while /(Perl|one|liner)/g' file1 file2 file3

Even though the point here is to make things even easier, most Perl one-liners
from the internet work, just by omitting "-e" or "-E".  A few differences are:
don't "goto LINE", but "next LINE" is fine.  In "-n" "last" goes straight to
the next file instead of being like "exit".  And shenanigans with unbalanced
braces won't work.
