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

my $q = new CGI;
my @result;

# other stuff happens

if ($q->param('command') eq "command1")
{
    # Notice how I pass NOTHING to the
    # system command that was handed to 
    # the CGI script.
    @result = `/usr/local/bin/script.sh`;
}
elsif ($q->param('command') eq "command2")
{
    # command 2...
}
#  more stuff happens.

# Include code to render your html around here
# then display the result of your system command here:
print join "<BR>", @result;
# Close out your html document.