#!/usr/local/bin/perl
use strict;
no strict 'vars';
use warnings;
use Scalar::Util 'reftype';

undef $/;
my $s = eval <STDIN>;
print $@ ? $@ : "(pp `".lisp( $s ).")\n";

sub lisp {
	# This is an utter, ugly hack. Please pretend you never saw it.
	my $thing = shift;
	my $type = reftype( $thing );

	no warnings 'uninitialized';
	if ( 'HASH' eq $type ) {
		# Returns an association list
		# ((KEY . VALUE)
		#  (KEY . VALUE)
		#  (KEY . VALUE))
		return '('. join( '', map { "($_ . ".lisp($thing->{$_}).')'} sort keys %$thing ) .')';
	}
	elsif ( 'ARRAY' eq $type ) {
		# Returns a list
		# (ELT ELT ELT ELT ELT)
		return '(' . join( ' ', map lisp( $_ ), @$thing ) . ')';
	}
	elsif ( not defined $type ) {
		# Returns bare numbers. I don't think I need to deal with underflow.
		return $thing if looks_like_float( $thing );

		# Returns bare numbers if I think they won't overflow
		return $thing if
			length $thing <= 9
			and looks_like_integer( $thing );

		return qq["\Q$thing\E"];
	}

	# Freely admit I can't handle anything fancy.
	die "Can't handle $type";
}

sub looks_like_float { shift =~ /^-?\d+\.\d+\z/ }
sub looks_like_integer { shift =~ /^-?\d+\z/ }