Perry's possessions indicate that he lives in a fantasy world. He imagines himself as a songwriter and a singer/guitarist, though he doesn't try to develop whatever musical talent he might possibly have. He carries his guitar—which he can barely play—with him and a trunk containing the songs he's written, despite knowing that he'll probably never have the opportunity to perform for an audience.

Another one of Perry's delusions is his intention to go treasure hunting. In his trunk is a "secret map" that Perry tells Dick will lead them to the sunken treasure of Captain Cortez that supposedly lies buried off the coast of Mexico.

Perry probably knows that all of this is nonsense. If he didn't, it's unlikely he would have gone along with Dick in the foolish (to put it mildly) scheme to rob the Clutters. The fact that they embark on this plan shows how disconnected from reality both of them are. Dick has no way of knowing if the Clutters even have a safe, basing his assumption entirely on the information another prison inmate gave him, and on the old "Kansas myth": that every farmer with a rich homestead has a safe containing tens of thousands of dollars in cash.

Perry, in spite of his delusions about himself, seems actually to be the more realistic of the two of them, and to know that the intended robbery will probably be a fiasco. He goes along with Dick, which is the clearest evidence that Perry knows that his own plans to build a life for himself through music or treasure-hunting are unworkable. He figures that he might as well gamble this attempted theft (which, unfortunately, ends in murder). The possessions Perry carries with him end up being junk.

Perry's possessions reveal a softness about his character as well as his need for human connection. Though Perry and Dick are a team, Perry's possessions separate him from Dick; they suggest that Perry is a sensitive soul, unlike Dick, whose cruelty and heartlessness are obvious to the reader.

Perry's attachment to his collection of letters and drawings is evidence of his deep capacity for emotion. The act of keeping and re-reading letters is an act that provides the recipient of the letters with comfort; that Perry might need comfort makes his character complex. Somehow, this collection of letters provides Perry with human warmth and reassurance, and his decision to keep the letters close by suggests that he wants these reminders near him at all times.

As well, Perry's collection of his own artwork reveals his creative and sensitive side. He enjoys drawing, and the fact that he keeps his drawings suggests that he is proud of his work. He says himself that he has beautiful penmanship, which also emphasizes Perry's concern for beauty and the aesthetic qualities of the world around him.

Perry keeps a variety of items with him in large boxes held together with string.  A lot of them are journals, letters, drawings, cards and other memorabilia.  He has letters from his sister encouraging him to be better than his brother and sister, who committed suicide.  He always has a letter from Floyd, who analyzes the letter for Perry, indicating that it's his sister that has problems, and not Perry.

One can tell from this that Perry is a pack rat who long to hold on to the past.  Perry's childhood was full of abandonment, death and crisis.  Perhaps he feels that if he holds on to these items, he can hold on to some of those people from his past.

The letter from Floyd show how much Perry is looking for acceptance (and may lead to why he hooked up with Dick in the first place.)  Though the letter from Perry's sister is well-meaning, Floyd spins it so that it seems as though Barab is the one with the problems and Perry isn't doing anything wrong.  From a childhood where Perry never knew who was going to be around, this acceptance is critical for him.