What will dumper do if I ask it for @_ within a sub? e.g.

T.I.T.S - Try It To See

$ perl -l
use Data::Dumper;
my $sql = " junk ";
Junk( $sql, 2,4 );
sub Junk {
    my @params = ($sql,@_);
    dbAction(@params);
}

sub dbAction(\@){
    print Dumper(@_);
    print Dumper(\@_);
}
^Z
$VAR1 = ' junk ';
$VAR2 = ' junk ';
$VAR3 = 2;
$VAR4 = 4;

$VAR1 = [
          ' junk ',
          ' junk ',
          2,
          4
        ];
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Dumper is breaking and I can't tell why.

That's because Dumper isn't breaking -- you've shown no proof