# use ${w}lc instead of $w\lc
# because $w\lc is makes \l make "c" lowercase!

$page_template =~ s/\Q$w$_$w/$input->param($_)/eg;
$page_template =~ s/\Q${w}lc_\L$_\E$w/$input->param(lc)/eg;
$page_template =~ s/\Q${w}uc_\U$_\E$w/$input->param(uc)/eg;