#!/usr/bin/perl -w
use strict;

{
    my( $quote7, $quote8, %quote, %unquote );
    BEGIN {
        $quote7= pack "C", 0x7e;        # Any 7-bit char.
        $quote8= pack "C", 0x7f;        # Any _other_ 7-bit char.
        @quote{ $quote7, $quote8 }=
            ( $quote7.$quote7, $quote7.$quote8 );
        @quote{  map  { pack "C", $_ }  0x80..0xff  }=
                 map  { $quote8 . pack "C", $_ }  0..0x7f;
        %unquote= reverse %quote;
    }
    sub strip8 {
        my( $bin )= @_;
        $bin =~ s#([$quote7$quote8\x80-\xff])#$quote{$1}#go;
        return $bin;
    }
    sub restore8 {
        my( $str )= @_;
        $str =~ s#([$quote7$quote8].)#$unquote{$1}#gos;
        return $str;
    }
}

die "Usage: $0 file\n"   if  1 != @ARGV;
open IN, "<$ARGV[0]"  or  die "Can't read $ARGV[0]: $!\n";
binmode IN;
undef $/;
my $in= <IN>;
my $out= strip8( $in );
my $end= restore8( $out );
die "Well, that didn't work!"   if  $in ne $end;