Copy the text of the script and run it in Perl. You'll have to reset the name of "test.txt" to a file in the same directory of your script, or you won't see any output.
# writeFile1.pl
# program opens a file, reads it, and prints
# the content to STDOUT and output file
# first, create a variable that holds the path to the source file
$source = "test.txt"; # assuming the file is in the same dir as the script
# second, create a variable that holds the path the output file
$target = "testOut.txt"; # creates the file in the same dir as the script
# third, create filehandles named 'SOURCE' and 'TARGET';
# TARGET is the output file; we have to specify whether
# we want the overwrite the file ==> (">$target")
# or append to the end of the file ==> (">>$target")
open(SOURCE, "<$source"); # < is optional for reading files
open(TARGET, ">$target"); # > overwrites existing file
# >> appends to existing file
# get input from SOURCE
while (<SOURCE>)
{
# we have two output filehandles, STDOUT and TARGET;
# STDOUT is default, so 'print' will go to STDOUT;
# to put output to TARGET, we have to specify
# 'print TARGET'
print STDOUT $_;
print TARGET $_;
}
print "\n\n";
close(SOURCE); # for good measure
close(TARGET);