Fasta specific length and position trimming

[Ernestas101]

Hello,

i'm fairly new to perl and got an issue with my practice work. So, here i go.
I got fasta file converted to plain sequence in .txt file like this - "FSNKSYLPSTTPEPLKKLRKEELE...".
I need to trim at specific positions, let's say: 4 and 8 => 4-KSYL-8. Just like that. Any help would be greatly appreciated, thank you.

[mastal]

fasta specific length and position

try the perl function substr()