perl -pi -e 's/$string_to_be_removed//g' full_path/one.txt

##</code><code>##

#!/usr/bin/perl
BEGIN {(*STDERR = *STDOUT) || die;}
use diagnostics;
use warnings;
use strict;
$| = 1;
my $file =  full_path/one.txt;
@ARGV = $file;
$^I = '~';
while (<>)
{
binmode ARGVOUT if $. == 1;    s/$string_to_be_removed//g;    
print;
}