# typical hash-of-hashes: my %hash = ( a => { b => 2 }, c => { b => 4 } ); $hash{$key1}{$key2} = $value; ##

##

  while ( my ( $outer_key, $outer_value ) = each %hash )
  {
      while ( my ( $inner_key, $inner_value ) = each %$outer_value )
      {
          # do whatever...
      }
  }

##

##

  # with dups
  my @inner_keys = map { keys %$_ } values %hash;

  # without dups
  my @uniq_inner_keys = do
  {
      my %inner_keys;
      while ( my ( undef, $href ) = each %hash )
      {
          @inner_keys{ keys %$href } = ();
      }
      keys %inner_keys;
  };

##

##

perl -lwe 'sub f { my $n = shift;
                   return $n < 2 ? 1 : $n * f($n-1); }
           print f(7);
           eval { print f(8); };
           if ( $@ ) { print "eval failed: $@" }'

##

##

#!/bin/bash -x

cp mutated-orig.plx mutated1.plx

for i in 1 2 3 4
do
    this=mutated$i.plx

    echo ';' >> $this
    echo 'if ( $@ ) { print "eval: $@" }' >> $this

    perl -MO=Deparse $this | ./mut-dewhack.plx > m$i.pre-parse
    perl $this > m$i.out 2> m$i.err
    perl -MO=Deparse $this | ./mut-dewhack.plx > m$i.post-parse

    next=mutated$(( $i + 1 )).plx
    cp $this $next
done;

##

##

./mutated1.plx: eval: line 1: unexpected EOF while looking for matching `"'
./mutated1.plx: eval: line 2: syntax error: unexpected end of file
./mutated1.plx: line 4: syntax error near unexpected token `.'
./mutated1.plx: line 4: `('`'|'-').('['^'"').('{'^'[').'\\$'.('`'|'-').('['^'#').('{'^'[').'='.('{'^'[').('^'^('`'|')')).('^'^('`'|'.')).('^'^('`''

##

##

  cmd1 arg1 arg2 arg3 && \
    cmd2 arg arg arg pirate arg arg arg

##

##

  foreach d in $( find . -type d -depth 1 -print )
  do
    tar czf $d.tar.gz $d && \
      rm -rf $d
  done

##

##

$ perl -lwe '$_="[http://a|alpha] [http://b|beta]";
             print;
             s{\[(http://.+?)\|(.+?)\]}
              {$2}gi;
             print'
[http://a|alpha] [http://b|beta]
alpha beta

##

##

$ perl -lwe '$_="[http://a|alpha] [http://b|beta] [http://g]";
             print;
             s{ \[ (http://.+?)
                   (?: \| (.+?) )? \] }
              { qq!! .
                (defined $2 ? $2 : $1) .
                qq!\n! }giex;
             print'
[http://a|alpha] [http://b|beta] [http://g]
alpha
 beta
 http://g

##

##

$ perl -lwe \
  '$_="[http://a|alpha] [http://b|beta] [http://g]";
   print;
   # match with title
   s{\[(http://[^\]\|]+)\|([^\]]+)\]} {$2\n}gi;
   # match without title
   s{\[(http://[^\]\|]+)\]}           {$1\n}gi;
   print'
[http://a|alpha] [http://b|beta] [http://g]
alpha
 beta
 http://g

##

##

  my $x = join("", 0..9)x2;
  my $lx = length($x);
  my $next_mult = ($lx + 15) & ~0x0f;
  $x .= "*" x ($next_mult - $lx);
  print "|$x|\n"'

##

##

=item $self->add_manufacturer( %args );

Adds a manufacturer to the database.  Required keys
in %args:

  company_id
  company_name
  address
  city
  state
  zip
  contact
  phone
  fax
  email
  account_number

Returns the new manufacturer id.

=cut

sub add_manufacturer
{
    my ( $self, %args ) = @_;

    # make sure we have all required keys
    my @cols = qw( company_id company_name
                   address city state zip
                   contact phone fax email
                   account_number );
    if ( my @missing = grep { ! exists $args{$_} } @cols )
    {
        die "add_manufacturer: missing args @missing";
    }

    # build up the SQL.  to make more efficient, do
    # this only once and stash it somewhere.
    my $cols   = join ',', ( 'id', cols );
    my $places = join ',', ( '?' ) x ( 1 + @cols );
    my $sql = "INSERT INTO sf_manufacturers ( $cols )" .
              "  VALUES ( $places )";

    # do the actual insertion here.
    $self->{dbh}->do( $sql, {}, undef, @args{@cols} );

    # still need to get actual new id here...
    return $self->{dbh}->get_latest_insert_id();
}

##

##

=item my $prefix = shortest_prefix @strings;

Return the shortest prefix common to all @strings.  Returns empty
string if there is no prefix; returns C if there are no strings
or if any of the values are themselves C

=cut

# algorithm by Ilya Z
# implementation by Ken Fox
# both ganked from c.l.p.misc:
# http://groups.google.fm/groups?selm=199908100340.UAA13944%40long-lake.nihongo.org

sub common_prefix ( @ )
{
    defined( my $prefix = shift )   or return undef;

    my $len = length $prefix        or return '';

    foreach my $w ( @_ )
    {
        defined $w                  or return undef;

        while ( substr( $w, 0, $len ) ne $prefix )
        {
            --$len;
            chop $prefix;
        }

        $len                        or return '';
    }

    return $prefix;
}

##

##

  SELECT *
    FROM my_table AS t,
         ( SELECT MAX( date ) AS max_date
             FROM my_table ) AS s
    WHERE t.date = s.max_date;

##

##

  #include 
  int max_int = std::numeric_limits::max();

##

##

  href="...&session=&mod=&..."

##

##


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