Sure, I've been playing with them today in the garden, so they're still fresh in my memory.
If you're on a typical Linux box, by the way, try
man 7 regex
from the command line for a listing of how posix regex works.
Anyway, what you want is:
$s = 'Here is some text, with a link in it...';
$s.= '<a href="%URL%" class="%ANYTHING%">More pages from %URL%</a>';
$s.= 'And a little more after it.';
$s = eregi_replace('<a href.*</a>','',$s);
print $s;