my $prog = 'myprog';
my $file = 'myfile';
my @useropts = qw(-bar -baz);

my @args = ("/path/to/$prog", '-foo', @useropts, $file, '-o', "$file.out");

print "system(): @args\n";  # debug
system (@args);

# vs.

print join(" ", "system():", "/path/to/$prog", '-foo', @useropts, $file, '-o', "$file.out"), "\n";  # debug
system("/path/to/$prog", '-foo', @useropts, $file, '-o', "$file.out");