Basically, I think dragonchild has it right. The "trick" is to build the map expression piece by piece. I'm unclear about the use of the array @file. If you are reading data from a file, or line by line in some way, and loading it into @file, you might consider processing the file directly as

use strict;
use warnings;

my @tmp01 = ();
    
push @tmp01, map{ $_."\n"} split " " while <DATA>;

exit;

__DATA__
foo bar
   munch
bar
foo bar
[download]

The split " " construct ensures that the function splits on whitespace, /\s+\, after skipping any leading whitespace although when I tried split with and without the " " argument, it worked correctly both ways.