my $start = 12;
my $end   = 27;

#my $substring = substr $string, $start - 1, $end - 1;

#Ooops, that should be:
my $substring = substr $string, $start - 1, $end - ( $start - 1 );
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First, read the perl docs (try perldoc -f substr). You would use substr. In your case, the code would look like:

use strict;
use warnings;  # always a good idea

my $start = 12;
my $end   = 27;

my $string = 'a string at least 27 characters long with any random cha
+racters';

my $substring = substr($string, $start, ($end - $start));
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So you are using 1 based numbering and you need to do the following:

use strict;
use warnings;

my $seq= 'ABCDEFGHIJKLM';
my $start=5;
my $end=7;

print substr $seq, $start - 1, ($end - $start) + 1;
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Prints:

EFG
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---

DWIM is Perl's answer to Gödel

You've had about 3 people explain to you how to get the length of a string given its start and end points. What more do you need?

emc

"Being forced to write comments actually improves code, because it is easier to fix a crock than to explain it. "
—G. Steele