aborted due to compilation error

Shell Programming and Scripting
1

I wanted to edit the time for a cron job that cleans out the quarantine in mailscanner.

etc/cron.daily/clean.quarantine

I edited the file

#!/usr/bin/perl


#
# IMPORTANT NOTE:
#
# Change the next line to 0 instead of 1 to enable this script.
# By default it will be disabled and will not do anything.
#

#$disabled = 0;



$quarantine_dir = '/var/spool/MailScanner/quarantine';
days_to_keep   = 7;

exit if $disabled;

Changed the days to keep to 7 instead of 30 and then enabled the script.

When I ran the script I got the following error

 cron.daily]#  ./clean.quarantine
Can't modify constant item in scalar assignment at ./clean.quarantine line 16, near "7;"
Execution of ./clean.quarantine aborted due to compilation errors.

What could of caused the script to bomb like that?
FYI I used vi to edit the file.

Thanks

2 
days_to_keep   = 7;

should be

$days_to_keep   = 7;
3

DUH
thanks
i figured it was something that simple