...
my $pid = fork;
if ( !defined $pid ) { 
    # maybe report an error to the browser...
}
elsif ( $pid == 0 ) {
    exec( 'wrapper_script', 'recipient@email', @other_args );
}
else {
    # print a simple HTML page to the client, saying that the job is
    # running and results will be emailed as soon as the job finishes
}
__END__