I'm biased toward Tk. I probably would have made 2 side by side text boxes and just cut'n'paste. The mouse would make it easier to cut in a mid-line position.Something like this (it even has built-in ctrl-c and ctrl-v key bindings)

#!/usr/bin/perl
use Tk;
use Tk::TextUndo;
use Tk::Adjuster;
use strict;

my $file = shift || $0;
my $buf;
open (FH,"< $file");
read( FH, $buf, -s FH );
close FH;

my $mw = tkinit(-title=>'Some Title');
my $TextTOP = $mw->Scrolled("TextUndo")->pack(-expand=>1, -fill=>'both
+');
my $adj = $mw->Adjuster->packAfter($TextTOP);
my $TextBOTTOM = $mw->Scrolled("Text")->pack(-expand=>1, -fill =>'both
+'),

$mw->bind('<Control-s>', sub { print "saving...\n" });
$mw->bind('Tk::Text', '<Control-s>', \&save_file);
$mw->Button(-text=>'Exit', -command=> sub{Tk::exit})->pack();

$TextTOP->insert('end',"$buf");


MainLoop;

sub save_file{
    open(FH,">> $0.txt") or warn "$!\n";
    my $current_text = $TextBOTTOM->get('1.0', 'end');
    print FH  $current_text,"\n";
    close FH;
  }
[download]