I don't believe that $_[1] is going to tell the routine column_exists to get the second element of @data -- it's going to pass the second element of $_, whatever that may be. It's a different context -- that's why my solution used 1 instead.

Down in the subroutine, @{$_[0]}[1] will select the second element of the first parameter (as an array reference), which is close to $_[1] but still not the same thing.

--t. alex

"Here's the chocolates, and here's the flowers. Now how 'bout it, widder hen, will ya marry me?" --Foghorn Leghorn

Somehow the desire to use $_[0] within routines (or anywhere, for that matter) has never tempted me. Why not just declare and use a my variable?