libString is simple textbox engine with some basic key combos:
Ctrl + C - Copy selected text
Ctrl + V - Paste text / Replace selected text with paste
Ctrl + A - Select whole line
Ctrl + X - Cut text
Enter - submit text and execute script (use libString_SetScript to set script for active textbox)
Backspace / Del / Home / End - Present too.
End User Licence Agreement (EULA).