Question

I am learning regular expression in perl, and i would like to have a function similar as bellow:

sub RegEx() 
{
  my $T = "0,1,";
  my $T2 = "-0:0-0:1-0:2-0:3-0:4-1:0-1:1-1:2-1:3-";

  printf ("T= %s <br>", $T);
  printf ("T2 %s <br>", $T2);

  my @values = split(',', $T);
  foreach my $val (@values) {
         printf ("We are at item %s in T <br>", $val);
         my $temp = $val .":" . "\(\\d\)\+";
         printf ("Rexeg %s <br>",$temp);
         @result = split(/$temp/, $T2);
         foreach my $val2 (@result) {
                printf ("T2- %s <br>", $val2);
         }
   }
}

and have the value of $T2 parsed to an array based on an index ($T)

but The following is being displayed

T= 0,1 
T2 -0:0-0:1-0:2-0:3-0:4-1:0-1:1-1:2-1:3- 
We are at item 0 in T 
Rexeg 0:(\d)+ 
T2- - 
T2- 0 
T2- - 
T2- 1 
T2- - 
T2- 2 
T2- - 
T2- 3 
T2- - 
T2- 4 
T2- -1:0-1:1-1:2-1:3- 
We are at item 1 in T 
Rexeg 1:(\d)+ 
T2- -0:0-0:1-0:2-0:3-0:4- 
T2- 0 
T2- - 
T2- 1 
T2- - 
T2- 2 
T2- - 
T2- 3 
T2- - 

Kindly let me know why i am still seeing

1. T2- -0:0-0:1-0:2-0:3-0:4- when the regular expression is 1:(\d)+

2. “-”

as the output of @results?

Answer 1

split makes no sense. You don’t want to split a string. You want:

my @result = $T2 =~ /$temp/g;

You really should include the “-” in your pattern. (Consider what happens when the numbers get to 10.)

my @result = $T2 =~ /-\Q$val\E:(\d+)/g;

(\Q..\E is technically no needed if $val is always going to be digits, but it’s a good habit.)

That said, I’d probably just parse $T2 once.

my $T2 = "-0:0-0:1-0:2-0:3-0:4-1:0-1:1-1:2-1:3-";
my %T2; push @{ $T2{$1} }, $2 while $T2 =~ /-(\d+):(\d+)/g;
...
my @result = @{ $T2{$val} };