Mlerm can be used in the situation where one does not have the answer to a question, but decides to give an answer in the form of a silly noise - mlerm.
This can be attributed to a hum and the small flicker of a tongue. This can be compared to "um", but is not a replacement.
When a reptile sticks its tongue out for a fast moment, either to smell something, lick something, or eat something. This most commonly happens in Bearded Dragons and Geckos but can happen uncommonly in mammals and amphibians. It can also be a sign of love from the animal.
Example 1
Rebecca: Are you going to mlerp the cricket?
Bearded Dragon: *mlerp*
Rebecca: Awww, want another buddy?
Example 2 Crested Gecko: *mlerp*
Steve: Did he mlerp you?
Carson: Yeah
Steve: Aww, that means she loves you!