for ( @whatever ) {
    if ( 1 .. 4 ) { 
        # enter this block during the first four iterations, then never again
    }
}

##</code><code>##

$_ = 0;
while ($_<6) {
  $_++;
  if ( 1 .. 4 ) { print "$_: True\n"; next; }
  print "$_: False\n";
}

__OUTPUT__ 
1: False
2: False
3: False
4: False
5: False
6: False

##</code><code>##

$_ = 0
while ($_<6) {
  $_++;
  if ( 0 .. 3 ) { print "$_: True\n"; next; }
  else { print "$_: False\n"; }
}

__OUTPUT__
1: True
2: True
3: True
4: True
5: True
6: True