$matchtext1 = "http://www.new.site/somenewpage.pl\?";
print "$matchtext1\n";
$matchtext2 = 'http://www.new.site/somenewpage.pl\?';
print "$matchtext2\n";

##</code><code>##

s/somenewpage.pl??/somenewpage.pl?/

##</code><code>##

$matchtext = "http://www.foo.bar/somepage.pl?";
$substitutetext = "http://www.new.site/somenewpage?";
s/\Q$matchtext\E/$substitutetext/;