this is a hack, no warranty whatsoever!

$tcl_data =~ s/([^{}\s]+)/'$1',/g;    # quote words + comma
$tcl_data =~ s/{/[/g;                 # start list
$tcl_data =~ s/}/],/g;                # end list + comma

#print $tcl_data;

my @perl_arr = eval($tcl_data);       # interpret as Array of AoAoA...

use Data::Dump 'pp';

pp @perl_arr;
[download]

thats the output

(
  [
    [
      "Register",
      [
        ["CumulativeActive(calls)(In)", 0],
        ["CumulativeSuccessfullyEstablished(calls)(In)", 0],
        ["CumulativeSuccessfullyCompleted(calls)(In)", 0],
        ["CumulativeUnsuccessful(calls)(In)", 0],
      ],
    ],
  ],
  [
    [
      ["Make", "Cal", "l"],
      [
        ["CumulativeActive(calls)(In)", 0],
        ["CumulativeSuccessfullyEstablished(calls)(In)", 0],
        ["CumulativeSuccessfullyCompleted(calls)(In)", 0],
        ["CumulativeUnsuccessful(calls)(In)", 0],
      ],
    ],
  ],
  [
    [
      "Initiating",
      [
        ["CumulativeActive(calls)(In)", 0],
        ["CumulativeSuccessfullyEstablished(calls)(In)", 0],
        ["CumulativeSuccessfullyCompleted(calls)(In)", 0],
        ["CumulativeUnsuccessful(calls)(In)", 0],
      ],
    ],
  ],
  [
    [
      "Summary",
      [
        ["CumulativeActive(calls)(In)", 0],
        ["CumulativeSuccessfullyEstablished(calls)(In)", 0],
        ["CumulativeSuccessfullyCompleted(calls)(In)", 0],
        ["CumulativeUnsuccessful(calls)(In)", 0],
      ],
    ],
  ],
)
[download]

you might wanna dig in and try to identify "arrays of two element arrays where the first element is a scalar" ( the "definition" of keyed lists), to convert them into hashes in the next step.