my $n = 10; 
while( $n ){ 
    print $n--;
    next if $n%2;
    ## do other stuff here
} continue{ 
    sleep 1;
}

##</code><code>##

my $n = 10; 
while( $n ){ 
    print $n--;
    unless( $n%2 ) {
        ## do other stuff here
    }
    sleep 1;
}