To extract substrings of given strings, use substr. I used the concatenation operator . combined with the assignment operator =, see perlop for details. 
#! /usr/bin/perl
use warnings;
use strict;

my $country  = 'Pakistan';
my $province = 'Punjab';
my $region   = 'Asia';

my $counter = 1;

my $sequenceid = substr $region, 0, 1;
$sequenceid   .= substr $country, 0, 2;
$sequenceid   .= substr $province, 0, 2;
$sequenceid   .= sprintf '%07d', $counter;

$sequenceid = uc $sequenceid;
print $sequenceid, "\n";

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To get a file path from the user, use Tk::FileSelect or Tk::getOpenFile.

Most of the contents of your post was irrelevant to the question. Please, try to study Short, Self Contained, Correct Example to learn how to ask good questions. 

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

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In reply to Re: Problem in perl/tk by choroba
in thread Problem in perl/tk by AMMAR

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