[c for c in %history if c.startswith('plot')]
[l for l in _ih if l.startswith('plot')]
Similar to the first answer you can do the following:
However, when iterating through the command history items you can do the following. Thus you can create your list comprehension from this.
for item in _ih: print item
This is documented in the following section of the documentation: http://ipython.org/ipython-doc/dev/interactive/reference.html#input-caching-system