pero四则运算

#!/usr/bin/perl
use v5.16;
my @tokens = <DATA> =~ m/(\d+|[\+\-\*\/\\(\)])/mxsg;


sub mycal{
my @tokens = @_;
my @stack;
while (@tokens) {
    my $token = shift @tokens;
    given ($token) {
        when (/[\*\/]/) {
           my $next = shift(@tokens);
           if ($next eq '(')
         {
               $next = mycal(get_tokens(\@tokens));
         }
           push @stack, cal($token,pop(@stack),$next);
        }
        when ('(') {
           push @stack, mycal(get_tokens(\@tokens));
        }
        default {
           push @stack, $token;
        }
    }
}
my @result;
while (@stack) {
    my $token = shift @stack;
    given ($token) {
        when (/[\+\-]/) {
           push @result, cal($token,pop(@result),shift(@stack));
        }
        default {
           push @result, $token;
        }
    }
}
return $result[0];
}

say mycal @tokens;

sub cal{
   my ($op, $lval, $rval) = @_;
   given ($op) {
       when ('+') {
           return $lval + $rval;
     }
       when ('-') {
           return $lval - $rval;
     }
       when ('*') {
           return $lval * $rval;
     }
       when ('/') {
           return $lval / $rval;
     }
   }
}

sub get_tokens {
    my $numl = 1;
    my $numr = 0;
    my $ref = shift;
    my @result;
    while ($numl != $numr) {
        my $cur = shift @$ref;
        given ($cur) {
            when ('(') {
                $numl ++;
            }
            when (')') {
                $numr ++;
            }
        }
        push @result, $cur;
    }
    pop @result;
    return @result;
}
__DATA__
(5 * (1 + 2)) * (1 + 1)