import re
def testReplaceBetweenWords():
 
    head_dlmt='Head'
    tail_dlmt='Tail'
 
    line0 = "abc_Head_def_Head_inner_inside_Tail_ghi_Tail_jkl"
    line1 = "abc_Head_first_Tail_ghi_Head_second_Tail_opq"
 
    between_pattern = "^((?:(?!{1}).)*{0}).*?({1}.*)$".format(head_dlmt, tail_dlmt)
    print(between_pattern)
    compiled_pattern = re.compile(between_pattern)
 
    # Case 0: good case: It captures the first inner words.    
    result0 = re.search(compiled_pattern, line0)  
 
    print("original 0    : {0}".format(result0.group(0)))
    print("expected Head : abc_Head_def_Head")
    print("found Head    : {0}".format(result0.group(1)))
    print("expected Tail :                                Tail_ghi_Tail_jkl")
    print("found Tail    : {0}{1}".format(' ' * (result0.regs[2][0]), result0.group(2)))
 
    print()
 
    # Case 1: Bad case: It captures the last pair words.    
    result1 = re.search(compiled_pattern, line1)
 
    print("original 1    : {0}".format(result1.group(0)))
    print("expected Head : abc_Head")
    print("found Head    : {0}".format(result1.group(1)))
    print("expected Tail :                Tail_ghi_Head_second_Tail_opq")
    print("found Tail    : {0}{1}".format(' ' * (result1.regs[2][0]), result1.group(2)))
 
print(testReplaceBetweenWords())

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