From the lines and expected outputs you have shown it looks like you want a character range from within a string. You can use substr for this. Note that Perl uses zero-based offsets into strings.

$ perl -E '
> $line = q{abcdefghijklmno};
> say $line;
> say substr $line, 0, 3;
> say substr $line, 5, 6;
> say substr $line, 13;'
abcdefghijklmno
abc
fghijk
no
$
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I hope this is helpful.