You could use grep to determine if the element already exists in the array. However it may be easier to use a hash. If the items you are working with are simple scalars (aka not references) assigning them as keys in a hash will assure you end up with a unique list. If you do not want to go that way, I have a few standard subroutines I use to find unique elements from a list. One (which is faster) will only work for simple string values, the second will work even when the list contains references. Here they are:

#_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
+-_-_-_-_
#   Function:  uniqStrings()
#   Author:  Dave Mueller
#   Returns:     @uniq
#   Parameters:  @array
#   Description: Returns a unique list of all Strings found in @array
#                Note: references wil be broken . . .
#_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
+-_-_-_-_
sub uniqStrings
{
        my %temp = ();
        @temp{@_} = ();
        return keys %temp;
}

#_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
+-_-_-_-_
#   Function:  uniqValues()
#   Author:  Dave Mueller
#   Returns:     @uniq
#   Parameters:  @array
#   Description: Returns a unique list of all values found in @array
#_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
+-_-_-_-_
sub uniqValues
{
        my %temp = ();
        @temp{@_} = (0 .. $#_);
        return map({$_[$_]} values %temp);
}
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