Since clipboard is being used, it is obvious that X is being used. Issue of appending to clip board regularly occurs. If you are not using Linux, following is not for you. My solution consists of two additional programs, xclip and xbindkeys. Please see the following shell script which can be bound to a desired key combination in xbindkeys. Simply select the desired text and press the key combination to append the selection to the clipboard.
#!/bin/sh
APPND=1
if [ $# -gt 0 ] ; then
if [ $1 -eq 1 ] ; then
APPND=0
else
APPND=1
fi
fi
if [ $APPND -eq 1 ] ; then
echo "$(/usr/bin/xclip -o -selection clipboard) $(/usr/bin/xclip -o -selection primary)"|/usr/bin/xclip -i -selection clipboard
else
echo "$(/usr/bin/xclip -o -selection primary) $(/usr/bin/xclip -o -selection clipboard)"|/usr/bin/xclip -i -selection clipboard
fi
Note: The above script is used to either insert in clipboard before of after its contents. the corresponding entries in my xbindkeys file is
"<complete path to the script>"
Shift+Alt+c
"<complete path to the script> 1"
Shift+Alt+d
So after selection, if we press Shift+Alt+c the selection is pasted at the end of the clipboard and if we press shift+Alt+d the selection is pasted before the current contents of the clipboard. Execute permissions should be given to the script. This is a universal solution for all x applications. I have verified it in gvim also.