my %allowed_text_code = ('$\\alpha$'     => 'α',
                         '$\\beta$'      => 'β',
                         '$\\gamma$'     => 'γ',
                         '$\\delta$'     => 'δ',
                         '$\\theta$'     => 'θ',
                         '$\\pi$'        => 'π',
                         '\\degrees'   => '°'
                         );

##</code><code>##

 foreach $tex_key (keys %allowed_text_code){
        $text =~ s/\Q$tex_key\E/$allowed_text_code{$tex_key}/g;
        print $text. "\n";
        }