1、词性不同
Perhaps是副词，用来做转折语的。maybe是动词。
Perhaps I may be permitted a few suggestions
也许我可以提几条建议。
The men were maybe a hundred feet away and coming closer.
那些人大约有100英尺远，正在向这里靠近。
2、位置不同
maybe要用于句首，perhaps可用于句末、句中、句首。
Perhaps, in time, the message will get through
或许消息会及时送达。
Things are maybe not as good as they should be
情况也许并没有情理之中那么好。
3、所用的场合不同
maybe为美国英语，主要用于非正式场合；perhaps请求及温和的命令，英国用法，用于正式场合。
He was not perhaps physically the strongest in the class.
他可能不是全班身体最壮的。
Wait a while, maybe a few days.
等一等吧，也许要过几天。