use strict;
my $str = 'Our website is <a href="www.me.com">www.me.com</a>
Our website is <a href="me.com">me.com</a>
Our website is <a href="http://www.me.com">http://www.me.com</a>
Our website is <a href="https://www.me.com">https://www.me.com</a>';
my $regex = qr/(https?:\/\/|(www\.)?[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,5}(:[0-9]{1,5})?(\/.*)?)/mp;
my $subst = '[x]';
my $result = $str =~ s/$regex/$subst/rg;
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