You could open a filehandle to read the nmap command and read each line in a loop. That way your script receives the command output, not the user, and you can parse the results and sanitise them for consumption by your clients. Something like

use strict;
use warnings;

my $nmapCmd = q{/path/to/nmap -and -any -args};
open my $nmapFH, q{-|}, $nmapCmd
   or die qq{fork: $nmapCmd: $!\n};

while ( <$nmapFH> )
{
    chomp;
    # Do something with nmap output here
    ...
    print qq{Sanitised stuff for user\n};
}

close $nmapFH
   or die qq{close: $nmapCmd: $!\n};
[download]

I hope this is of use.

Cheers,

JohnGG