| 
| Hand waving....
| 
|

# be sure to close the files before re-opening them if they have been opened in the script
# prior to this point
open(F1,"> file1.txt") or die "file1.txt: $!";
open(F2,"< file2.txt") or die "file2.txt: $1";

|
|  More hand waving....

$line=<F2>;   # read a line from file2.txt
print F1 $line; #write that line to file1.txt