PERL: Regex Pattern (": ")

I have a text file containing some JSON content. The file is really big and it containing more than 1,00,000 lines. So manual extraction is not fair. I have written the PERL script to read each line of the file, which meets my need.

Sample Text file : Sample.txt

  "key": "Programming",
  "doc_count": 1

  "key": "Base",
  "doc_count": 1,

  "key": "Experience",
  "doc_count": 1

  "key": "Electrophoresis",
  "doc_count": 1

I would like to take the key value alone covered within double brackets, say Programming, Base, Experience and Electrophoresis.

PERL script tried: ExtractKeyValue.pl

use strict;
use warnings;

my $file = $ARGV[0];
open my $info, $file or die "Could not open $file: $!";

while( my $line = <$info>)  {
    if($line =~ /"key(.*)",/){
        print $1;
        print "\n";
        }
}

close $info;

By using this, I am getting the output like,

": "Programming
": "Base
": "Experience
": "Electrophoresis

I don't want that ": ". I have tried like, $line =~ /"key: "(.*)",/. But it is not working. The command executes but no output and no error symptoms.

G:\ExtractKeyValue_Regex>perl ExtractKeyValue.pl Sample.txt > Output_Sample.txt

G:\ExtractKeyValue_Regex>

The output should be like,

Expected Output:

Programming
Base
Experience
Electrophoresis

I could not figure out why the colon(:) and space and double quotes is not tracked by the pattern.

Any suggestion would be helpful!