Here is a commandline and a Tk front end to a bash shell interpreter. A select loop would replace the Tk event loop's fileevent in the cmd version.

#!/usr/bin/perl
use warnings;
use strict;
use IPC::Open3;
use IO::Select;

my $pid = open3(\*WRITE, \*READ,\*ERROR,"/bin/bash");

my $sel = new IO::Select();

$sel->add(\*READ);
$sel->add(\*ERROR);

my($error,$answer)=('','');

while(1){

 print "Enter command\n";
 chomp(my $query = <STDIN>);
 
 #send query to bash
 print WRITE "$query\n";

 foreach my $h ($sel->can_read)
 {
   my $buf = '';
   if ($h eq \*ERROR)
   {
     sysread(ERROR,$buf,4096);
     if($buf){print "ERROR-> $buf\n"}
   }
   else
   {
     sysread(READ,$buf,4096);
     if($buf){print "$query = $buf\n"}
   }
 }
}

waitpid($pid, 1);
# It is important to waitpid on your child process,  
# otherwise zombies could be created.
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And the Tk version:

#!/usr/bin/perl
use warnings;
use strict;
use Tk;
use IPC::Open3;
require Tk::ROText;

$|=1;

my $mw = new MainWindow;

my $entry=$mw->Entry(-width => 80)->pack;

$mw->Button(-text => 'Execute',
        -command => \&send_to_shell)->pack;

my $textwin =$mw->Scrolled('ROText',
       -width => 80,
       -bg =>'white',    
       -height => 24,
       )->pack;

$textwin->tagConfigure( 'err', -foreground => 'red' );

my $pid = open3( \*IN, \*OUT, \*ERR, '/bin/bash' ) or warn "$!\n";

$mw->fileevent( \*OUT, readable => \&read_stdout );
$mw->fileevent( \*ERR, readable => \&read_stderr );

$entry->bind('<Return>',[\&send_to_shell]);
$entry->focus;

MainLoop;

sub read_stdout {
    
    if( sysread( OUT, my $buffer, 1024 ) > 0 ){
       $textwin->insert( 'end', $buffer );
       $textwin->see('end');
      }
}

sub read_stderr {
    if( sysread(ERR, my $buffer, 1024 ) > 0 ){
      $textwin->insert( 'end', $buffer, 'err' );
      $textwin->see('end');
    }
}

    
sub send_to_shell {
   my $cmd= $entry->get();
   print IN "$cmd\n";
}
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