# get the indexes of items in an array
@foo{ @foo } = 0 .. $#foo;
$foo{'abc'} # the index of 'abc' in @foo

# dragonchild id=376694
sub unique { my %x; grep { !$x{$_}++ } @_ }

# broquaint id=374287
sub in_list {return !!grep { $_ eq $_[0] } @_[ 1 .. $#_ ];}
# ysth
sub in_list {my $target=shift; return !!grep { $_ eq $target } @_} 

# demerphq
sub find_first_index {
  my $target=shift;
  push @_,$target;
  my $i=0;
  $i++ while $_[$i] ne $target;
  return $i==$#_ ? undef : $i
}