[Veronica Loell]'s "Mimers brunn" [http://mimersbrunn.sourceforge.net]
project includes a message extractor for use with
[msgcat].  It also knows how to translate to the
po-format of GNU gettext.
----
An few example tcl-rows:

 .lblfileName configure -text\
 [::msgcat::mc "Make sure that the folder you want to repair\n\
 is not currently in use, and then select it by clicking 'Select folder'."];#! This is a message to the translator

Will produce the following entry:

 #. widget: label - This is a message to the translator
 #: src/uidrebuild.tcl:33
 ::msgcat::mcset sv\
 "Make sure that the folder you want to repair\n\
 is not currently in use, and then select it by clicking 'Select folder'."\
 \

----
Converted to po-format (after translation):

 #. widget: label
 #: src/uidrebuild.tcl:33
 msgid ""
 "Make sure that the folder you want to repair\n"
 "is not currently in use, and then select it by clicking 'Select folder'."
 msgstr ""
 "Se till att foldern du vill reparera\n"
 "inte �r �ppen, och v�lj den sedan genom\n"
 "att klicka p� 'V�lj folder'"
----
And back to msgcat again:

 #. widget: label
 #: src/uidrebuild.tcl:33
 ::msgcat::mcset sv\
 "Make sure that the folder you want to repair\n\
 is not currently in use, and then select it by clicking 'Select folder'."\
 \
 "Se till att foldern du vill reparera\n\
 inte �r �ppen, och v�lj den sedan genom\n\
 att klicka p� 'V�lj folder'"\