print that string to either STDOUT or MYFILE depending on how I call a print function.

print { $to_file ? *MYFILE : *STDOUT } $str;
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ikegami -

How do I define *MYFILE? I've been doing it using open(MYFILE,'>>out.txt'); But to write to that file, it has to be opened, written to, and then closed. So I'm not sure how to define MYFILE prior to calling the print_to() function. Would it now be a file handle, and pass something like $fh to the subroutine? I don't know what words to use to look up more about your method of passing variables using the ? and :

Sounds like you want ambrus's 3rd solution

# Open log file once
open(MYFILE, '>>', $qfn)
    or die("Cannot open file $qfn for appending: $!\n");

...

print_to($to_file ? *MYFILE : *STDOUT, $str);
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Better yet, use a lexical

open(my $MYFILE, '>>', $qfn)
    or die("Cannot open file $qfn for appending: $!\n");

...

print_to($to_file ? $MYFILE : *STDOUT, $str);
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Finally, if you want to reopen the file every time you call print_to,

my $MYFILE;
if ($to_file) {
    open($MYFILE, '>>', $qfn)
        or die("Cannot open file $qfn for appending: $!\n");

    print_to($to_file ? $MYFILE : *STDOUT, $str);
} else {
    $MYFILE = *STDOUT;
}

print_to($MYFILE, $str);
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