use POSIX;

...
    my $datedname = join('_', $servername, strftime("%m%d%Y", localtime());
    my %opts = (
        server => 'master',
        mk_image => 'yes',
        source => $servername,
        location => "$filepath/$servername/$datedname",
        );

    my @cmd = qw/nim -o define -t mksysb/;
    for my $o ( keys %opts ) { push @cmd, '-a', "$o=$opts{$o}" }
    push @cmd, $datedname;
    print " command-line:  @cmd\n";
    system( @cmd );
}