Loops

  LINE: while( $line = <SESAME>){
    ....
      last LINE if $line eq "\n";
    ...
      next LINE if $line =~ /^#/; # skip comment lines
    }
#
# arrays in scalar context return length
#
  while( @ARGV) 
    {
      process( shift @ARGV);
    }
#
# 
#
  for( $i=0; $i < 10; $i = $i + 1)
    {
    ...
    }
#
# $elem is a reference, not a copy, i.e.: 
# changing $elt changes @list
#
  foreach my $elt (@list)
    {
    ...
    }
#
# $i in [0, 100]
#
  foreach my $i (0 .. 100)
  {
  ...
  }
#
# keys of a hash table
#
  foreach $key (sort keys %hash)
    {
    ...
    }