You can also generate the unpack string from the header itself if you know that the position of the keys in the header defines the columns in the rest of the file:

#!/usr/bin/perl

use strict;
use warnings;

my $header = <DATA>;
my @p;
push @p, length $1 while $header =~ /(\S+\s*)/g;
my $unpack_pattern = join "", map { 'A'.$_ } @p[0..$#p-1];
$unpack_pattern .= "A*";

while (<DATA>){
  chomp;
  my @vals = unpack($unpack_pattern,$_);
  print join "|", @vals,"\n";
  #$sth->execute(@vals);
}

__DATA__
StudentId Name      Dept address                 city
1         Chellappa CSE  22 xx-colony 2nd street coimbatore
2         Vijay     IT   23 yy colony            coimbatore
[download]

There is a CPAN module DataExtract::FixedWidth for handling the fixed unpacking details. I tried it on the test sample and it seems to work fine.

use strict;
use warnings;

use DataExtract::FixedWidth;
use Data::Dumper;

my $de = DataExtract::FixedWidth->new({
    header_row => scalar(<DATA>)
});
while (my $l = <DATA>) {
    my $fields = $de->parse($l);
    print Dumper($fields);
}

__DATA__
StudentId Name      Dept address                 city
1         Chellappa CSE  22 xx-colony 2nd street coimbatore
2         Vijay     IT   23 yy colony            coimbatore
[download]

Ron

StudentId | Name | Dept | address | city |

+-----------+--------+--------+-----------+------------------------+

| 1 | a CSE | 22 x | x-colony | 2nd street coimbatore |

| 2 | T 23 | yy col | ony coim | batore

when i am trying this code only above values to store database for example CSE is not stored in dept column