use strict;
my $str = '<div id="attachment_3340" style="width: 865px" class="wp-caption alignnone">
<img class="size-full wp-image-3340" alt="Testbild" src="https://beispiel.de/images/Testbild.jpg" width="855" height="631" />
<p class="wp-caption-text">© Copyright</p>
</div>';
my $regex = qr/(<p>|<div .*>)(\s*)(<a .*>)?(\s*)(<img .* \/>)(\s*)(<\/a>)?(\s*)(<p .*>.*<\/p>)?(\s*)(<\/p>|<\/div>)/p;
my $subst = '$3$5$7$9';
my $result = $str =~ s/$regex/$subst/r;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html