my %COLUMNS = (
    MY_FIRST_TABLE => [ qw( blah_1 blah_2 ) ], 
    MY_2ND_TABLE   => [ qw( another_col dob ) ], 
    . . . 
);

# $table defined elsewhere
my $SQL = 'SELECT ' . join(',', @{ $COLUMNS{$table} }) . " FROM $table";