open (FH, "file.txt")  or die "$!";
undef $/;
$slurped_file = <FH>; # whole file resides in $slurped file now.
open (CFH, ">copied_file.txt") or die "$!";
print CFH $slurped_file;
# file.txt contents now reside in copied_file.txt.
# close your filehandles.