my $xpid = 1234;

%procs = map { $_ => 1 } @{ $dbh->selectall_arrayref( "select spid from v\$process" ) };

if ( $procs{ $xpid } ) {
   print "Pid is in use : $xpid\n";
}



##</code><code>##

my $xpid = 1234;

@procs{ @{ $dbh->selectall_arrayref( "select spid from v\$process" ) } } = ();

if ( exists $procs{ $xpid } ) {
   print "Pid is in use : $xpid\n";
}