He's putting all the elements of the array into a hash, using a hash slice @check{@arr} = @arr x 1;

Then, if there is only one key, all the values must have been identical.

@check{@arr} is the "keys" part of the slice, and @arr x 1 just gives us the correct number of "values."

Voila! A list of the unique elements of @arr (in keys %check). If there is only one unique element, then they are all the same. Two problems solved for the price (two lines, in this case) of one. :-)

Russ
Brainbench 'Most Valuable Professional' for Perl