Мишка, Гришка, Пощипай ехали на лодке...

There are different ways words develop their meaning in a language. There is a phenomenon called 'etymological doublets' or sometimes 'triplets', when in a language there are several words with somewhat different meanings, even though they have the same original source or root. The reason they have different meanings and look different is that because they entered the language as borrowings from different languages at different times. Typical examples of doublets in English are captain and chieftain, chief and chef, frail and fragile.

There is an interesting process going on at the present moment with one of the Russian verbs which very well may lead to the creation of a pair of doublets, even though strictly speaking they will not qualify as real doublets since they will develop not by being borrowed from different languages, but through their incorrect conjugation in the Russian vernacular - просторечие.

There are several Russian verbs which add the letter "л" ("l") in the middle when they are conjugated, and which do not have it in the infinitive. They do create a certain difficulty for foreigners learning Russian. But unless the letter "l" appears only in the first person singular and nowhere else (like in the verbs любить - люблю - любит; копить - коплю - копят; топить - топлю - топят) such verbs may create a certain difficulty even for native Russian speakers. I would like to look at 3 such verbs: КАПАТЬ, СЫПАТЬ and ЩИПАТЬ.

The verb КАПАТЬ can be conjugated both, with the intruding "l" letter and without it. Both ways are correct and listed in dictionaries: КАПАЮ, КАПАЕШЬ and КАПЛЮ, КАПЛЕШЬ. The only thing that can be added here is that the variant with "l" may sound a little outdated, it is rarely used nowadays and even in the dictionary the example comes from an old idiom: НЕ КАПЛЕТ НАД КЕМ-ЛИБО.

The verb СЫПАТЬ can only be conjugated with the letter "l" in the middle: СЫПЛЮ, СЫПЛЕШЬ. С утра СЫПЛЕТ мокрый снег. I have to admit, that even though this is the only correct variant of conjugating this verb, not everybody remembers it and quite a few people incorrectly  say СЫПЕТ, СЫПЕШЬ, СЫПЯТ instead. One can imagine that in 50 or 100 years from now the variant without "l" in the middle may become a new norm.

But the most interesting thing is happening to the verb ЩИПАТЬ. The correct way to conjugate it is WITH the "l" in the middle: ЩИПЛЮ, ЩИПЛЕШЬ, ЩИПЛЕТ, ЩИПЛЕМ, ЩИПЛЕТЕ, ЩИПЛЮТ. This correct variant is used quite infrequently nowadays. Unfortunately, even some (not to say many) educated people omit the letter "l". It is even registered in dictionaries as "colloquial". Now, what is really interesting, is that there are 2 ways of conjugating this verb, when used in просторечие - vernacular (I would still prefer to say it is vernacular, rather than colloquial speech). It all depends on the meaning. If what is meant is "TO PINCH", people usually say: ЩИПАЮ, ЩИПАЕШЬ, ЩИПАЕТ, ЩИПАЕМ, ЩИПАЕТЕ, ЩИПАЮТ (-СЯ can be added): Не щипайся! А Ваня щипается! Пощипай его! If what is meant is "TO STING" or "TO BURN", especially in impersonal sentences, people usually say:  ЩИПЕТ (again, -СЯ can be added):  Мазь сильно ЩИПЕТ. В горле ЩИПЕТ. Мороз ЩИПЕТ уши. 

So what we get here is a sort of doublets with identical infinitive forms but different conjugation patterns depending on the meaning! In English, for example, there is no such verb which would mean both "to pinch" and the burning or stinging sensation on the skin. May be in Russian, again, in 50 or 100 years from now these will be different verbs?