$somethingelse="AA";
$var = 'BB';
$_ = 'beforeBBafter';
s@$var@$somethingelse@;
print; #prints "beforeAAafter"

##</code><code>##

$somethingelse="AA";
$var = '<a href="somefilename(x)withanumberedhash.htm#666">';
$_ = 'before<a href="somefilename(x)withanumberedhash.htm#666">after';
s@$var@$somethingelse@;
print;

##</code><code>##

$somethingelse="AA";
$var = '<a href="somefilename\(x\)withanumberedhash.htm#666">';
$_ = 'before<a href="somefilename(x)withanumberedhash.htm#666">after';
s@$var@$somethingelse@;
print;