I am getting the following error when I run the code,strangely if set the variable as $8k_m,if I remove the number "8" and change the variable as "$k_m",I see the error is gone,what am I doing wrong?

Error:-

Bareword found where operator expected at ftp.pl line 15, near "$8k_m"
        (Missing operator before k_m?)
Can't use global $8 in "my" at ftp.pl line 15, near "my $8"
syntax error at ftp.pl line 15, near "$8k_m"
Execution of ftp.pl aborted due to compilation errors.


#!/usr/bin/perl -w 
use strict;  
use warnings; 
use Cwd qw(getcwd);
use File::Copy;
use File::Find;
use Net::Telnet;
use Net::FTP;
use Getopt::Std;

my %options=();
getopt("b",\%options);

my $cwd = getcwd;
my $8k_m= $options{b};

my ($input,$output);



my %files = map {$_ => 1} qw(amss.mbn dsp.elf);

find(sub {
    copy($File::Find::name, $cwd) or die "Can't cp $File::Find::name: 
+$!"
        if (delete $files{$_});
}, $8k_m);

print "\nFTP.ing Modem and DSP images...\n";
my $ftp = Net::FTP->new("10.42.9.119", Debug => 0)
or die "Cannot connect to the target: $@";

$ftp->login("user","user")
or die "Cannot login ", $ftp->message;

$ftp->cwd("/mnt/data")
or die "Cannot change working directory ", $ftp->message;

$ftp->binary();

$ftp->put("data.mbn") or die "put failed ", $ftp->message;;
$ftp->put("file.elf") or die "put failed ", $ftp->message;
$ftp->quit();
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