こちらのファイルを改造して、ファイルの書き込みをするようにしました。
Apache2 の PHP で virtual を使う

次のフォルダーに書き込みます。

/var/log/apache2/php
/var/log/apache2/perl

test_virtual.php

<?php
// ------------------------------------------------------------------
//	test_virtual.php
// ------------------------------------------------------------------
// fputs ('STDERR',"*** start ***\n");
// fputs (STDERR,"*** aaa ***\n");
$fp_out = fopen('/var/log/apache2/php/php_aa.log', 'w');
fputs ($fp_out,"*** test_virtual.php *** start ***\n");
fputs ($fp_out,"*** bbb ***\n");
fputs ($fp_out,"*** ccc ***\n");
fputs ($fp_out,"*** ddd ***\n");
fputs ($fp_out,"*** Mar/22/2021 PM 17:09 ***\n");
fputs ($fp_out,"*** test_virtual.php *** end ***\n");
fclose ($fp_out);

echo '<!DOCTYPE html>';
echo '<html  lang="ja">';
echo "<head>";
echo '<meta http-equiv="CONTENT-TYPE" content="text/html; charset=utf-8" />';
echo "<title>virtual</title>";
echo "</head>";
echo "<body>";
echo "<h2>test_virtual.php</h2>";
echo exec('whoami');
echo "<p></p>";
echo "<p>Mar/22/2021 PM 15:30</p>";
echo "</body>";
echo "</html>";
?>

test_script.pl

# ! /usr/bin/perl
#
#	test_script.pl
#
print STDERR "*** test_script.pl *** start ***\n";
print STDERR "*** Mar/22/2021 PM 15:38 ***\n";
#
print "Content-type: text/html; charset=utf-8\n\n";
print "*** test_script.pl ***<br />\n";
print "Hello<br />\n";
print "Good Morning<br />\n";
print "Mar/22/2021 PM 15:59<br />\n";
print "<p></p>\n";
#
#
$file_out = "/var/log/apache2/perl/perl_aa.txt";
open (OUT,">$file_out");
binmode OUT, ":encoding(UTF-8)";
print OUT "*** test_script.pl *** start ***\n";
print OUT "*** test ***\n";
print OUT "*** Mar/22/2021 PM 17:13  ***\n";
print OUT "*** test_script.pl *** end ***\n";
close (OUT);
#
print STDERR "*** test_script.pl *** end ***\n";
#