To log to file without modifing all your existing prints use select to make print automatically go to a filehandle.

use FileHandle;

my $log = 0;
print "Do you want to log to a file?";
my $resp = <STDIN>;
if ($resp =~ /^y/i) {
    my $fh = new FileHandle;
    my $filepath = "c:\\stdout.txt";
    $fh->open(">> $filepath") || die "could not open log file $filepat
+h";
    select $fh;
}

#
# this will go to log file if $resp was y
#
print "Holla!\n";
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-HTH