Why do you consider sexeger preferable to ordinary regexes for this? 
sub my_epe {
  my ($s,$h) = @_;
  my $op = '(' . join('|', keys %$h) . ')';
  my $con = qr/Con (\d+(?:\.\d+)?)/;
  1 while $s=~s/$op \s+ $con \s+ $con/'Con '.$h->{$1}($2,$3)/ex;
  $s;
}

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In reply to Re: Parsing/Evaluating a prefix-notation equation using sexeger by Roy Johnson
in thread Parsing/Evaluating a prefix-notation equation using sexeger by jryan

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