use Class::ParmList qw(simple_parms);

sub convert {
   my ($from, $to, $thing) = simple_parms([qw(from to thing)], @_);

   #...
}

##</code><code>##

use Sub::Parms;

sub convert {
    BindParms : (
        my $from  := from;
        my $to    := to;
        my $thing := thing;
    )
    
    #...
}