试编写一个模式匹配算法，匹配过程为：先匹配模式的首尾字符，若匹配成功，调用成员函数Substr（取子串）来检查模式的首尾之间的字符是否与目标的相应字符相匹配，若匹配不成功；则进行下一次匹配。

你可以参考下面的伪代码来理解这个简单的模式匹配算法，它通常用于正则表达式的实现中，如KMP算法（Knuth-Morris-Pratt算法）：

def pattern_match(text, pattern):
    n = len(text)
    m = len(pattern)
    
    # 创建部分匹配表 (Partial Match Table, PMP)
    pmp = [0] * (m + 1)
    j = -1
    for i in range(1, m + 1):
        while j != -1 and pattern[i] != pattern[j + 1]:
            j = pmp[j]
        if pattern[i] == pattern[j + 1]:
            j += 1
        pmp[i] = j
    
    i, j = 0, 0
    while i < n:
        if text[i] == pattern[j]:
            i += 1
            j += 1
        else:
            if j != 0:
                j = pmp[j]
            else:
                i += 1
                
    return j == m

def substr_check(text, pattern, start, end):
    return text[start:end+1] == pattern

# 主程序示例
text = "ababcaba"
pattern = "abca"

if pattern_match(text, pattern):
    print("Pattern found.")
    match_start = text.find(pattern)
    print(f"Substring check at position {match_start}: {substr_check(text, pattern, match_start, match_start+len(pattern) - 1)}")
else:
    print("Pattern not found.")