Code
regex
cat|dog cat or dog
(ab|cd)ef abef or cdef
gr(a|e)y gray or grey
^(From|Subject): line starts with From: or Subject:
\b(cat|dog)\b whole word cat or dog
(?|a(b)|c(d)) branch reset (PCRE)Match one of several branches.
cat|dog cat or dog
(ab|cd)ef abef or cdef
gr(a|e)y gray or grey
^(From|Subject): line starts with From: or Subject:
\b(cat|dog)\b whole word cat or dog
(?|a(b)|c(d)) branch reset (PCRE)