use File::Temp "tempfile"; 
my($T, $N) = tempfile("perm-XXXXXXXX", UNLINK => 1); 
say $T "SignPerm(PermList(1+[", join(",", @p), "]));\n"; 
close $T or die; 
my $s = qx"gap -q <$N"; 
if (1 == $s) { say "even" } elsif (-1 == $s) { say "odd" } else { die }