Consider also B::perlstring(), which not only handles escaping, but also adds the quote characters...

#!/usr/bin/perl -l
use B;

while (<>) {
  chomp;
  print B::perlstring($_) if /^[\$\w]+$/;
}
[download]

The B module is bundled with Perl itself, so you already have it. The perlstring() function was added in Perl 5.8, so this will not work on Perl 5.6.