Can I commit only parts of my code using SVN or Mercurial?

% hg record
diff --git a/prelim.tex b/prelim.tex
2 hunks, 4 lines changed
examine changes to 'prelim.tex'? [Ynsfdaq?]
@@ -12,7 +12,7 @@
 setmonofont[Scale=0.88]{Consolas}
 % missing from xunicode.sty
 DeclareUTFcomposite[UTFencname]{x00ED}{'}{i}
-else
+else foo
 usepackage[pdftex]{graphicx}
 fi

record this change to 'prelim.tex'? [Ynsfdaq?]
@@ -1281,3 +1281,5 @@
 %% Local variables:
 %% mode: latex
 %% End:
+
+foo
 No newline at end of file
record this change to 'prelim.tex'? [Ynsfdaq?]  n
Waiting for Emacs...

% hg di
diff --git a/prelim.tex b/prelim.tex
--- a/prelim.tex
+++ b/prelim.tex
@@ -1281,3 +1281,5 @@
 %% Local variables:
 %% mode: latex
 %% End:
+
+foo
 No newline at end of file