1 files changed, 37 insertions, 27 deletions

diff --git a/challenge-143/wlmb/perl/ch-1.pl b/challenge-143/wlmb/perl/ch-1.pl
index cc18d4ac91..80c20d3932 100755
--- a/challenge-143/wlmb/perl/ch-1.pl
+++ b/challenge-143/wlmb/perl/ch-1.pl
@@ -6,33 +6,42 @@
 use v5.12;
 use warnings;
 use Scalar::Util qw(looks_like_number);
+use Try::Tiny;
 my $original_string;
+my $previous;
 my $current;
-my $next;
+my $token;
 foreach (@ARGV){
-    my $original_string=$current=$_;
-    token();
-    my $result=expression();
-    say "$original_string=$result";
+    try {
+        $original_string=$previous=$current=$_;
+        token();
+        my $result=expression();
+        die "Extra characters: $previous\n" if defined $token->[0];
+        say "$original_string=$result";
+    }
+    catch {
+        warn $_;
+    };
 }
 
 sub token {
-    $next=[$1,$1], return if $current=~s{^\s*([()*/+-])}{}; # symbol
-    $next=['N',$1], return
+    $previous=$current;
+    $token=[$1,$1], return if $current=~s{^\s*([()*/+-])}{}; # symbol
+    $token=['N',$1], return
         if $current=~s{^\s*([^()*/+\-\t\n ]*)}{}
            and looks_like_number($1); # number?
-    $next=[undef,undef], return if $current=~/^\s*$/; # nothing
-    die "Unrecognizable input: $current";
+    $token=[undef,undef], return if $current=~/^\s*$/; # nothing
+    die "Unrecognizable input: $previous\n";
 }
 
 sub expression {
     my $result=term();
     while(1){
-	my $op=$next->[0];
-	last unless defined $op && $op=~m{[+-]};
-	token();
-	$result+=term(),next if $op eq '+';
-	$result-=term(),next if $op eq '-';
+        my $op=$token->[0];
+        last unless defined $op && $op=~m{[+-]};
+        token();
+        $result+=term(),next if $op eq '+';
+        $result-=term(),next if $op eq '-';
     }
     return $result;
 }
@@ -40,24 +49,25 @@ sub expression {
 sub term {
     my $result=simple();
     while(1){
-	my $op=$next->[0];
-	last unless defined $op && $op=~m{[*/]};
-	token();
-	$result*=simple(),next if $op eq '*';
-	$result/=simple(),next if $op eq '/';
+        my $op=$token->[0];
+        last unless defined $op && $op=~m{[*/]};
+        token();
+        $result*=simple(),next if $op eq '*';
+        $result/=simple(),next if $op eq '/';
     }
     return $result;
 }
 sub simple {
-    my $op=$next->[0];
-    my $val=$next->[1];
-    die "Unrecognized expression: $current" unless defined $op && $op=~/[-(N]/;
+    my $op=$token->[0];
+    my $val=$token->[1];
+    die "Unrecognized expression: $previous\n" unless defined $op && $op=~/[-+(N]/;
     token();
-    return -simple() if $op eq '-';
-    return $val if $op eq 'N';
-    my $result=expression();
-    $op=$next->[0];
-    die "Unbalanced parenthesis: $current" unless defined $op and $op eq ')';
+    return -simple() if $op eq '-'; # unary -
+    return simple() if $op eq '+';  # unary +
+    return $val if $op eq 'N';      # number
+    my $result=expression();        # parenthesized expression
+    $op=$token->[0];                # closing parenthesis should follow
+    die "Unbalanced parenthesis: $previous\n" unless defined $op and $op eq ')';
     token();
     return $result;
 }