$_ = "OR=5AND=>1536463OR<foORobarOR=5 ";
while (m/(AND|OR)                     #either AND or OR
         (=[><=]?|[><]=?|!=|<>)       #one of = => =< == > < >= ....
         (                            #capture all within...
           (?:                        #  group for quantifier
             (?!                      #      not followed by
               (?:AND|OR)             #        AND or OR
               (?:=[><]?|[><]=?|[!=]=)#        one of = => =< ...
             )                        #      any of the inside
             .                        #      match any char..
           )+                         #  1 or more of the above
         )                            #and return it..
       /xgms) { #ignore spaces, repeated, 
                #multiline, . matches all
       # and if it all worked out then...
       print "$1 $2 $3\n";
}
# outputs
# OR = 5
# AND => 1536463
# OR < foORobar
# OR = 5