my %main_file; 
push @{ $main_file{ USER }[ 1 ] }, 'fred'; 
push @{ $main_file{ TEST }[ 3 ] }, 'bill'; 
push @{ $main_file{ TRIM }[ 0 ] }, 'john'; 

pp \%main_file;;
{
  TEST => [undef, undef, undef, ["bill"]],
  TRIM => [["john"]],
  USER => [undef, ["fred"]],
}